Dietary Supplements and Life Stages: Pregnancy

Introduction

Nutritional requirements change throughout a person's lifespan. During pregnancy, higher intakes of many nutrients are needed to support maternal health and proper fetal development [1].

This fact sheet summarizes current research and recommendations for vitamins, minerals, choline, and omega-3 fatty acids during pregnancy and focuses on key nutrient considerations during this life stage. It also covers several botanicals. Finally, it includes a special considerations section that covers twin and other multiple pregnancies, vegetarian diets, bariatric surgery, and sickle cell disease.

More detailed information about individual nutrients can be found in the Office of Dietary Supplement (ODS) vitamin and mineral supplement fact sheets and omega-3 fatty acids fact sheet.

Nutrient Intake Recommendations and Upper Limits

Intake recommendations for all essential nutrients are provided in the Dietary Reference Intakes (DRIs) developed by the Food and Nutrition Board (FNB) of the National Academies of Sciences, Engineering, and Medicine [1]. These values, which vary by age and sex, include the following:

• Recommended Dietary Allowance (RDA): Average daily level of intake sufficient to meet the nutrient requirements of nearly all (97%–98%) healthy individuals; often used to plan nutritionally adequate diets for individuals.
• Adequate Intake (AI): Intake at this level is assumed to ensure nutritional adequacy; established when evidence is insufficient to develop an RDA.
• Estimated Average Requirement (EAR): Average daily level of intake estimated to meet the requirements of 50% of healthy individuals; usually used to assess the nutrient intakes of groups of people and to plan nutritionally adequate diets for them; can also be used to assess the nutrient intakes of individuals.
• Tolerable Upper Intake Level (UL): Maximum daily intake unlikely to cause adverse health effects.

Recommended Intakes

Table 1 lists the current micronutrient RDAs and AIs during pregnancy [2-8]. If an entry is bolded, it means that the intake recommendation for that nutrient is higher during pregnancy. If an entry is not bolded, the intake recommendations are the same for pregnant and nonpregnant females of the same age.

Table 1: Recommended Dietary Allowances and Adequate Intakes During Pregnancy [2-8]
Bolded entries indicate values that are higher during pregnancy.

Nutrient	Age
	14–18 y	19–50 y
Biotin (mcg)	30*	30*
Boron	N/A	N/A
Calcium (mg)	1,300	1,000
Chloride (g)	2.3*	2.3*
Choline (mg)	450*	450*
Chromium (mcg)	29*	30*
Copper (mcg)	1,000	1,000
Fluoride (mg)	3*	3*
Folate (mcg DFE)	600	600
Iodine (mcg)	220	220
Iron (mg)	27	27
Magnesium (mg)	400	350–360**
Manganese (mg)	2*	2*
Molybdenum (mcg)	50	50
Niacin (mg Niacin Equivalents)	18	18
Omega-3 fatty acids (ALA only, g)	1.4	1.4
Pantothenic acid (mg)	6*	6*
Phosphorus (mg)	1,250	700
Potassium (mg)	2,600*	2,900*
Riboflavin (mg)	1.4	1.4
Selenium (mcg)	60	60
Sodium (mg)	1,500*	1,500*
Thiamin (mg)	1.4	1.4
Vitamin A (mcg RAE)	750	770
Vitamin B12 (mcg)	2.6	2.6
Vitamin B6 (mg)	1.9	1.9
Vitamin C (mg)	80	85
Vitamin D (mcg)	15	15
Vitamin E (as alpha-tocopherol, mg)	15	15
Vitamin K (mcg)	75*	90*
Zinc (mg)	12	11
* AI
** The magnesium RDA is 350 mg for ages 19 to 30 and 360 mg for ages 31 to 50.
Key: AI = Adequate Intake ALA = alpha-linolenic acid (the only omega-3 fatty acid that is classified as an essential nutrient) DFE = dietary folate equivalents N/A = not applicable (due to insufficient data to derive an intake recommendation) RAE = retinol activity equivalents RDA = Recommended Dietary Allowance

Upper Limits

Most nutrients have ULs that are based on levels of intake that may cause adverse health effects. Other nutrients do not have ULs due to a lack of data showing adverse effects at high intakes.

For folate, magnesium, niacin, and vitamin E, the ULs apply only to supplemental intakes (e.g., dietary supplements, fortified foods, medications), not dietary intakes of the nutrient naturally present in food [5-7]. For vitamin A, the UL applies only to preformed vitamin A, not beta-carotene or other provitamin A carotenoids. In all other cases, the ULs apply to total intakes, including dietary and supplemental intakes [8].

For omega-3 fatty acids, the FNB established an Acceptable Macronutrient Distribution Range for alpha-linolenic acid (ALA) of 0.6% to 1.2% of energy for anyone age 1 year and older [2].

Table 2 lists the current ULs during pregnancy [2-8]. The bolded entry for phosphorus indicates that this nutrient has a lower UL for females who are pregnant (3,500 mg) than for those who are not (4,000 mg). For all other nutrients, the ULs are the same for pregnant and nonpregnant females of the same age.

Table 2: Tolerable Upper Intake Levels (ULs) During Pregnancy [2-8]

Nutrient	Age 14–18 y	Age 19–50 y
Biotin	ND	ND
Boron (mg)	17	20
Calcium (mg)	3,000	2,500
Chloride (g)	3.6	3.6
Choline (mg)	3,000	3,500
Chromium	ND	ND
Copper (mcg)	8,000	10,000
Fluoride (mg)	10	10
Folate (supplemental only, mcg)	800	1,000
Iodine (mcg)	900	1,100
Iron (mg)	45	45
Magnesium (supplemental only, mg)	350	350
Manganese (mg)	9	11
Molybdenum (mcg)	1,700	2,000
Niacin (supplemental only, mg)	30	35
Omega-3 fatty acids (ALA)	N/A	N/A
Pantothenic acid	ND	ND
Phosphorus (mg)	3,500*	3,500*
Potassium	ND	ND
Riboflavin	ND	ND
Selenium (mcg)	400	400
Sodium	ND	ND
Thiamin	ND	ND
Vitamin A (as preformed vitamin A only, mcg)	2,800	3,000
Vitamin B12	ND	ND
Vitamin B6 (mg)	80	100
Vitamin C (mg)	1,800	2,000
Vitamin D (mcg)	100	100
Vitamin E (supplemental only, as alpha-tocopherol, mg)	800	1,000
Vitamin K	ND	ND
Zinc (mg)	34	40
* Phosphorus is the only entry in the table that has a lower UL during pregnancy.
Key:  ALA = alpha-linolenic acid N/A = not applicable (ALA does not have a UL, only an Acceptable Macronutrient Distribution Range) ND = not determinable (due to a lack of data of specific adverse effects) UL = tolerable upper intake level

Prenatal Supplements

As shown in Table 1, many nutritional requirements are increased during pregnancy. Consuming a variety of nutritious foods can help pregnant women obtain the nutrients needed for a healthy pregnancy.

Dietary supplements, including prenatal multivitamin/mineral supplements, can also help ensure sufficient nutrient intakes for a healthy pregnancy [9-13]. These products are hereafter referred to as “prenatal supplements.”

The American College of Obstetricians and Gynecologists (ACOG) recommends screening patients regarding their diet and supplement use to ensure they are meeting recommended intakes for calcium, iron, vitamin A, the B vitamins, vitamin D, and other nutrients [14]. ACOG and the Academy of Nutrition and Dietetics also recommend that pregnant women take a daily prenatal supplement [15,16]. The 2020–2025 Dietary Guidelines for Americans (DGA) notes that most health care providers recommend a daily prenatal supplement for women who are pregnant or are planning to become pregnant in addition to following a healthy dietary pattern [17]. The DGA adds that prenatal supplements may be especially important to meet folate/folic acid, iron, iodine, and vitamin D needs during pregnancy.

An analysis of data from the 2001–2014 National Health and Nutrition Examination Survey (NHANES) indicates that about 70% of pregnant women in the United States take a dietary supplement [18]. However, even after accounting for dietary supplement use, many pregnant women in the United States have inadequate intakes of some micronutrients [18,19]. According to an analysis of data from the U.S. Environmental influences on Child Health Outcomes (ECHO) consortium, pregnant women who are of Hispanic ethnicity or non-White race, have less than a high school education, are age 14 to 18 years, or have obesity are at higher risk than others of inadequate micronutrient intakes [19].

Prenatal supplements are available over the counter, or they can be prescribed by a health care provider, which makes them eligible for health insurance reimbursement [20]. However, no standard or federal statutory definition exists for prescription or nonprescription prenatal supplements in terms of the ingredients and doses they should contain [10,21]. Product formulations vary considerably, so it is important to consider both the ingredients and the doses in these products. For example, some prenatal supplements do not contain iodine [22], while others do not contain choline [23,24]. In other cases, the doses that are present in the product are lower than recommended amounts. For example, choline is often present in relatively small amounts in prenatal supplements [23]. Some prenatal supplements may not provide folate in the recommended form of folic acid for reducing the risk of neural tube defects (NTDs) [20]. Gummy formulations often contain no iron or calcium [25]. In addition, some prenatal supplements contain botanical and other ingredients, such as probiotics [11,12]. Many of these ingredients have not been thoroughly studied in pregnant women.

There are also formulation differences between prescription and nonprescription prenatal supplements. A 2017 evaluation of prenatal supplement labels in the United States found that prescription products contained a mean of 9 vitamins and 4 minerals, whereas nonprescription products contained a mean of 11 vitamins and 8 minerals [11]. In addition, prescription products had higher labeled amounts of folic acid compared with nonprescription products, whereas nonprescription products had higher labeled amounts of iodine, calcium, vitamin A, and vitamin D.

A 2023 analysis examined more than 20,000 dietary supplements on the U.S. market, including 421 prenatal supplements, to determine how labeled doses of six key nutrients during pregnancy (vitamin A, vitamin D, folate, calcium, iron, and long-chain omega-3 fatty acids) compare with “target doses” [26]. Target doses were derived by determining usual nutrient intakes via 24-hour dietary recalls and calculating optimal supplementation doses to shift 90% of participants to intakes above the EARs while keeping 90% of participants below the ULs. Out of the 69 products that contained all six nutrients, only one product, which was not a prenatal supplement, contained the target doses for those nutrients.

Clinicians should also be aware that the actual doses in prenatal products may differ from label values. A 2023 report from the U.S. Government Accounting Office that examined 12 over-the-counter prenatal supplement products found that 11 of the 12 products contained at least one nutrient with an amount outside acceptable deviations from the label value, based on U.S. Pharmacopeia thresholds [21]. There were also trace amounts of lead or cadmium in 6 of the 12 prenatal supplements tested, although not in amounts likely to cause a health concern based on U.S. Food and Drug Administration (FDA) metrics.

In addition, an analysis of 51 samples from 26 prenatal supplements that are commonly used in Canada, including one prescription brand, found that 14 samples contained doses of lead that exceeded the limit set by California Proposition 65 and the U.S. Pharmacopeia (>0.5 mcg/day) [27]. Three samples also exceeded known upper limits for aluminum and inorganic arsenic.

Choosing a product that has been tested by an independent quality assurance organization can help ensure that it was properly manufactured, contains the ingredients and doses listed on the label, and does not contain harmful levels of contaminants. Consumerlab.com, NSF, and U.S. Pharmacopeia are independent organizations that offer dietary supplement quality testing [10].

Key Nutrient Considerations Before and During Pregnancy

Obtaining the recommended amounts of all nutrients is important for a healthy pregnancy. Certain nutrients have critical roles before and during pregnancy and may be underconsumed among pregnant women. These include calcium, choline, folate/folic acid, iodine, iron, magnesium, omega-3 fatty acids, vitamin A, vitamin B6, vitamin B12, vitamin D, and zinc. It is also important to note that excessive intakes of preformed vitamin A (but not beta-carotene or other provitamin A carotenoids) can be teratogenic [8].

The sections below provide a brief overview of each of these key nutrients; the recommended amounts and ULs during pregnancy; food and supplement sources; a summary of the research on dietary supplements and pregnancy; and, where available, clinical practice guidelines from professional societies, government agencies, and public health organizations. Nutrients are presented in alphabetical order.

Calcium

Overview

Calcium, the most abundant mineral in the body, comprises much of the structure of bones and teeth. It also mediates blood vessel contraction and dilation, muscle function, blood clotting, nerve transmission, and hormonal secretion [4,28]. Vitamin D promotes calcium absorption.

The RDA for calcium during pregnancy is 1,300 mg for ages 14 to 18 years and 1,000 mg for ages 19 to 50 years [4]. These values are the same as those for nonpregnant females in the same age ranges.

Good food sources of calcium include milk, yogurt, and cheese. Calcium is also present in some nondairy foods [4]. For example, certain vegetables such as kale, broccoli, and Chinese cabbage (bok choi) provide some calcium. In addition, some fruit juices and plant-based milk substitutes are fortified with calcium. However, the bioavailability of calcium from some plant-based foods is lower than that from milk products [29].

Calcium is available in many dietary supplements, including some prenatal supplements [12]. According to a 2021 evaluation of 188 prenatal supplements on the U.S. market, 78% of these products included calcium, with a median amount of 200 mg/serving [30]. Another evaluation of 214 products found that nonprescription prenatal supplements contained a mean of 368 mg of calcium, while prescription products contained a mean of 172 mg [11]. Gummy formulations often contain no calcium [25].

According to the 2020–2025 DGA, calcium is a nutrient of public health concern because it is underconsumed by the U.S. population [17]. Similarly, some pregnant women in the United States do not obtain sufficient amounts of calcium. An analysis of 2001–2014 NHANES data found that pregnant women age 20 to 40 years had a mean daily intake of calcium from foods of 1,093 mg, and 21.2% of them were consuming less than the EAR for calcium [18].

Dietary supplements that contain calcium can help pregnant women reach the recommended intake of calcium. These supplements may be particularly useful for women who do not regularly eat dairy products or calcium-fortified foods. This could include those who are lactose intolerant, have a milk allergy, or who follow a vegan diet [31]. However, as noted above, prenatal supplements typically contain relatively low amounts of calcium [11,30].

When total intakes, including dietary supplements, are considered, the mean daily calcium intake among pregnant women in the United States increases to 1,311 mg, and the percentage of women who fall below the EAR decreases to 12.9% [18]. Pregnant women who are age 14 to 18 years, races or ethnicities other than non-Hispanic White, or those who have less than a high school education may be more likely than others to have total calcium intakes from food and dietary supplements that are below the EAR, according to data from the ECHO consortium [19].

A small percentage of pregnant women in the United States might obtain too much calcium. The UL for calcium during pregnancy is 3,000 mg/day for ages 14 to 18 years and 2,500 mg for ages 19 to 50 years [4]. These values are the same as those for nonpregnant females. When total calcium intakes from foods and dietary supplements are considered, 3% of pregnant women age 20 to 40 years in the United States exceed the calcium UL according to 2001–2014 NHANES data [18].

Calcium and pregnancy

Obtaining the recommended amount of calcium during pregnancy is important for both fetal and maternal health because calcium is important for building and maintaining strong bones and teeth [4,32].

In addition, calcium supplementation during pregnancy might reduce the risk of gestational hypertension. It may also reduce the risk of preeclampsia, a serious condition characterized by hypertension and proteinuria that usually occurs after 20 weeks gestation [33,34]. However, research indicates that the benefit of calcium supplementation for reducing the risk of preeclampsia applies only to pregnant women with inadequate calcium intakes (such as those with intakes below 600 mg/day), so calcium supplementation for this purpose is usually recommended only in populations with low calcium intakes, such as those in many low- and middle-income countries. In addition, much of the evidence for calcium and preeclampsia comes from studies with methodological weaknesses [35,36].

A 2024 meta-analysis included 26 randomized controlled trials (RCTs) in 20,038 women that evaluated calcium supplementation during pregnancy [37]. In most of the RCTs, calcium supplementation was started before 24 weeks gestation. The analysis found the following:

• Calcium supplementation reduced the risk of preeclampsia by 49% and the risk of gestational hypertension by 30%.
• Calcium supplementation did not significantly affect other outcomes, including the risk of preterm delivery, small for gestational age, low birth weight, or perinatal or maternal mortality.

A 2022 systematic review and meta-analysis that included 30 trials in 20,445 women examined the effects of both high-dose (at least 1,000 mg/day) and low-dose (less than 1,000 mg/day) calcium supplementation on the risk of preeclampsia, [38]. About half of the trials were conducted in countries in Southeast Asia and the Western Pacific and Eastern Mediterranean regions. It found the following:

• Overall, both high-dose and low-dose calcium supplementation reduced the risk of preeclampsia by 51%.
• The effects of calcium supplementation did not differ based on baseline preeclampsia risk, vitamin D supplementation, or the time that calcium supplementation was initiated.
• Calcium supplementation did not affect preeclampsia risk in women with adequate baseline calcium intake (adequate intake not defined).
• Based on these findings, the authors concluded that low-dose calcium supplementation is as effective as high-dose supplementation. They also concluded that calcium supplementation should be recommended only for women with low calcium intake.

A 2018 Cochrane Review included 27 RCTs that evaluated the use of calcium supplements during pregnancy to prevent hypertensive disorders and related problems [39]. The RCTs were conducted in many different countries including Ecuador, India, Iran, and the United States. Thirteen trials in 15,730 women—none of which administered vitamin D supplements—evaluated high-dose calcium (at least 1,000 mg/day). Twelve trials in 2,334 women evaluated calcium doses that were less than 1,000 mg/day (usually 500 mg/day) either alone, or combined with vitamin D, linoleic acid, or antioxidants. The review found the following:

• High-dose calcium supplementation reduced the risk of high blood pressure by 35%. It also reduced the risk of preeclampsia by 55%, but subgroup analyses showed that the risk of preeclampsia was reduced only in those with low dietary calcium intakes (usually defined as less than 900 mg/day), not in those with adequate intakes. In addition, the quality of this evidence was low.
• Calcium supplementation of less than 1,000 mg/day reduced the risk of high blood pressure by 47% and preeclampsia by 62%. However, most of these trials recruited women who were at high risk of preeclampsia, and the trials had a high risk of bias.

Limited research has examined whether calcium supplementation during pregnancy helps prevent leg cramps. A Cochrane Review analyzed two studies that compared the use of calcium supplements to no intervention and one study that compared the use of calcium supplements to vitamin C [40]. Fewer women in the calcium groups had leg cramps than in the no intervention groups. However, there were no differences between groups for the composite outcome of leg cramp intensity and frequency. There was no difference in leg cramp frequency between women who took calcium and those who took vitamin C. The authors concluded that it is unclear whether calcium supplements reduce the incidence of leg cramps during pregnancy.

Calcium supplementation recommendations

Several professional societies and public health organizations recommend calcium supplements for pregnant women with low calcium intakes to reduce the risk of preeclampsia. These recommendations are summarized in Table 3.

Table 3. Recommendations for Calcium Supplementation During Pregnancy to Reduce the Risk of Preeclampsia

Source	Population	Recommendation	Notes
ACOG [35]	Pregnant women with calcium intakes of <600 mg/day	1,500–2,000 mg/day calcium supplementation	N/A
2020–2025 DGA [17]	All pregnant women	N/A	Calcium is a nutrient of public health concern because it is underconsumed by the U.S. population, including pregnant women.
WHO [41]	Pregnant women with low dietary calcium intakes	1,500–2,000 mg/day calcium supplementation	Divide calcium supplements into three doses. Calcium supplements should preferably be taken with meals. Separate taking calcium supplements from iron supplements by several hours.
The Canadian Hypertensive Disorders of Pregnancy Working Group [42]	Pregnant women with calcium intakes of <600 mg/day	≥1,000 mg/day calcium supplementation	N/A
International Society for the Study of Hypertension in Pregnancy [43]	Pregnant women with low calcium intakes	≥1,000 mg/day calcium supplementation	N/A
Society of Obstetric Medicine of Australia and New Zealand [44]	Pregnant women with moderate to high risks of preeclampsia, particularly those with low dietary calcium intakes	1,500 mg/day calcium supplementation	N/A
Key:  ACOG = The American College of Obstetricians and Gynecologists DGA = Dietary Guidelines for Americans N/A = not applicable WHO = World Health Organization

More information is available in the ODS calcium fact sheet for health professionals.

Choline

Overview

Choline is an essential nutrient that is required for the synthesis of phosphatidyl choline and sphingomyelin, two major phospholipids that are vital for cell membranes. All plant and animal cells need choline to preserve their structural integrity [6,45]. Choline also plays a role in cell membrane signaling, neurotransmitter production, nervous system function and early brain development, gene expression, and lipid transport and metabolism [6,45,46].

The AI for choline during pregnancy is 450 mg [6]. This value is higher than the AI for nonpregnant females, which is 400 mg for ages 14 to 18 years and 425 mg for ages 19 and older.

The main dietary sources of choline in the United States are animal-based products, including meat, poultry, fish, dairy products, and eggs. Other sources of choline include cruciferous vegetables, such as broccoli and brussels sprouts; soybeans; nuts; seeds; and whole grains [47-51].

Choline is available in many dietary supplements, but not all prenatal supplements contain choline [12]. A 2022 evaluation of 188 prenatal supplements on the U.S. market found that 40% of these products included choline, with a median amount of only 25 mg/serving [23].

Most pregnant women in the United States do not meet the recommended intakes of choline [17]. An analysis of 2001–2014 NHANES data found that pregnant women age 20 to 40 years had a mean daily intake of choline from foods of 321 mg, and only 7.7% of them had an intake above the AI for choline [18]. Contributions from dietary supplements do not add substantially to total choline intakes during pregnancy. Given the low amounts of choline in most prenatal supplements, total intakes from foods and dietary supplements among pregnant women in the United States are similar to that from food alone [18].

The risk of inadequate choline status in pregnant women might be greater in those who do not take folic acid supplements, those with low vitamin B12 status, and those with a genetic variant in the folate-metabolizing enzyme methylenetetrahydrofolate dehydrogenase [24,52]. Dietary supplements that contain choline can help pregnant women reach the recommended intake of choline and they may be particularly useful for people who follow a vegan diet or avoid eggs. However, as noted above, prenatal supplements typically contain only small amounts of choline [23], so it is important to check product labels to determine whether choline is present and what amount the product contains.

The UL for choline during pregnancy is 3,000 mg/day for ages 14 to 18 years and 3,500 mg for ages 19 to 50 years [6]. These values are the same as those for nonpregnant females. Limited data suggest that no pregnant women exceed the UL for choline when total intakes from foods and dietary supplements are considered [18].

Choline and pregnancy

Choline is important for fetal growth and the development of the central nervous system [10], but most pregnant women do not meet recommended intakes of choline during pregnancy [16,17]. Some studies have found associations between lower choline intakes and/or plasma or serum choline concentrations during pregnancy and an increased risk of NTDs, but not all studies agree with these findings [53-55]. Furthermore, plasma and serum choline concentrations are not good choline status indicators [53].

A meta-analysis of 5,570 pregnant women across five case-control studies conducted in the United States or Canada [53] found the following:

• There was a 36% higher risk of NTDs in the children of pregnant woman with low choline intakes or low circulating choline concentrations.
• For spina bifida specifically, there was a 33% higher risk in children of pregnant women with low maternal choline intake. There were no significant associations between material choline intake and the risk of anencephaly.
• However, the authors noted that the results should be interpreted with caution because of the limited number of studies included in the meta-analysis and possible recall bias.

Choline supplementation recommendations

Currently, there are no specific recommendations from professional societies, government agencies, or public health organizations for choline supplementation during pregnancy. However, as summarized in Table 4, consuming a variety of choline-containing foods is important during pregnancy, and supplementation may be warranted in some circumstances.

Table 4. Recommendations for Choline During Pregnancy

Source	Population	Recommendation	Notes
2020–2025 DGA [17]	All pregnant women	Consume a variety of choline-containing foods.	Most pregnant women do not meet the recommended intakes of choline.
	Pregnant women who follow a vegetarian or vegan diet	Consult with a health care provider to determine whether supplementation with choline is necessary.
The Academy of Nutrition and Dietetics [16]	All pregnant women	N/A	Choline is an essential nutrient during pregnancy. Most pregnant women do not obtain adequate amounts of choline.
Key:  DGA = Dietary Guidelines for Americans N/A = not applicable

More information is available in the ODS choline fact sheet for health professionals.

Folate/Folic Acid

Overview

Folate is a water-soluble B vitamin that occurs naturally as folate in foods, as folic acid in fortified foods and dietary supplements, and as other forms of folate in dietary supplements. Folate functions as a coenzyme or cosubstrate in single-carbon transfers during the synthesis of nucleic acids (DNA and RNA) and the metabolism of amino acids [6,56,57]. It is also required for proper cell division.

When consumed, folate undergoes a series of conversions to produce 5-MTHF, which is also known as L-5-MTHF, L-methylfolate, 5-methyl-folate, and methylfolate. This is the main active form of folate in plasma [56]. People with a genetic polymorphism, 677C>T, in the methylenetetrahydrofolate reductase (MTHFR) gene have a reduced ability to convert folate to 5-MTHF because the methylenetetrahydrofolate reductase enzyme needed for this conversion is less active [58]. About 25% of people who are Hispanic, 10% of people who are Caucasian or Asian, and 1% of people who are African American are homozygous for the 677C>T MTHFR polymorphism [59].

The RDA for folate during pregnancy is 600 mcg dietary folate equivalents (DFE), where 1 mcg DFE equals 1 mcg folate from food, 0.6 mcg folic acid from fortified foods or dietary supplements consumed with foods, or 0.5 mcg folic acid from dietary supplements taken on an empty stomach [6]. These values are higher than the value for nonpregnant females, which is 400 mcg DFE. Conversion factors between mcg DFE and mcg for supplemental folate in the form of 5-MTHF have not been formally established [60].

Folate is naturally present in vegetables (especially dark green leafy vegetables), fruits and fruit juices, nuts, beans, peas, seafood, eggs, dairy products, meat, poultry, and grains [56,61]. Folic acid is also added to enriched breads, cereals, flours (including corn masa flour), pastas, rice, and other grain products as part of the folic acid fortification program in the United States to reduce the risk of NTDs [62,63]. Other countries around the world also have folic acid fortification programs.

Folate, as either folic acid or 5-MTHF, is present in many dietary supplements [12]. This includes almost all prenatal supplements; according to a 2021 evaluation of 188 prenatal supplements on the U.S. market, 98% of these products included folate, with a median amount of 800 mcg/serving [30]. Another evaluation of 173 products found that nonprescription prenatal supplements contained a mean of 733 mcg (as mcg folic acid), while prescription products contained a mean of 1,062 mcg [20]. The form of folate used in prenatal supplements is an important consideration because the recommendations for reducing the risk of NTDs only apply to folic acid, not 5-MTHF [17,20,64]. According to a 2020 evaluation, approximately 32% of prescription prenatal products and 25% of nonprescription prenatal supplements on the U.S. market contain 5-MTHF [20].

Some pregnant women in the United States do not obtain sufficient amounts of folate from their diets. An analysis of 2001–2014 NHANES data found that pregnant women age 20 to 40 years had a mean daily intake of folate from foods of 630 mcg DFE, and 35.8% of them consumed less than the EAR for folate [18]. Dietary supplements that contain folate can help pregnant women reach the recommended intake. When total intakes, including dietary supplements, are considered, the mean daily folate intake among pregnant women in the United States increases to 1,451 mcg DFE and the percentage of women who fall below the EAR decreases to 16.4% [18].

Some pregnant women in the United States might obtain too much supplemental folate. The UL for supplemental folate during pregnancy is 800 mcg/day for ages 14 to 18 years and 1,000 mcg/day for ages 19 to 50 years. These values are the same as those for nonpregnant females and apply only to folate intakes from supplements and/or fortified foods, not folate that is naturally present in food [6]. According to 2001–2004 NHANES data, 33.4% of pregnant women age 20 to 40 years in the United States exceed the UL for supplemental folate [18]. Pregnant women who are non-Hispanic Black or non-Hispanic White may be more likely than those who are other races or ethnicities to have supplemental folate intakes that exceed the UL, according to data from the ECHO consortium [19].

Folic acid and pregnancy

Obtaining the recommended amount of folate before and during pregnancy is critical for proper embryonic and fetal development because of folate’s key role in cell division and nucleic acid synthesis.

Clear evidence from observational studies, clinical trials, and the folic acid food fortification program shows that a sufficient intake of folic acid before pregnancy and during early pregnancy (periconceptional intake) reduces the risk of NTDs [64-72]. Because NTDs occur within 28 days after conception when the neural tube closes, the critical window for folic acid intake runs from preconception through the first 28 days after conception. This is often before a woman is aware she is pregnant and may be prior to the first prenatal health care visit.

Folic acid acts as a methyl group donor in one-carbon metabolism. This may be a mechanism by which it helps prevent NTDs [73]. An analysis of data from the National Birth Defects Prevention Study indicates that higher intakes of other methyl donors and micronutrients that play a role in one-carbon metabolism, especially vitamin B6, vitamin B12, choline, betaine, and methionine, might further reduce NTD risk beyond folic acid alone [74].

Pregnant women with a 677C>T MTHFR polymorphism may have less biologically available 5-MTHF and, thus, reduced methylation potential, leading to an increased risk of NTDs [56,75]. A DNA analysis found that women who were homozygous for this polymorphism had a more than three times greater risk of having an infant affected by an NTD than those who were not [76]. Research on the effects of various forms of folate supplementation for women with this genetic polymorphism is ongoing [77,78]. A randomized trial in 60 pregnant women in Canada found that supplementation with 5-MTHF produced similar erythrocyte and serum folate concentrations as folic acid, while reducing maternal concentrations of unmetabolized folic acid [79]. However, the Centers for Disease Control and Prevention (CDC) still recommends supplementation with folic acid, not 5-MTHF, for those with MTHFR polymorphisms to reduce the risk of NTDs [80]. This is because 5-MTHF has not been tested in clinical trials for reducing the risk of NTDs; folic acid is the only form of folate that is currently proven to reduce the risk of NTDs.

Some research suggests that folic acid supplementation might reduce the risk of other birth defects, such as cleft lip, cleft palate, and congenital heart defects. However, the authors of a 2015 Cochrane Review of five trials in 7,391 women concluded that the data are insufficient to determine if periconceptional folic acid affects birth defects other than NTDs [72]. In addition, it is unclear whether folic acid supplementation affects the risk of autism spectrum disorder [65,66,81-84].

Folic acid supplementation recommendations

Numerous professional societies, government agencies, and public health organizations recommend folic acid supplementation both before and during early pregnancy to reduce the risk of giving birth to an infant with an NTD. These recommendations are summarized in Table 5.

Table 5. Recommendations for Folic Acid Supplementation Before and During Pregnancy to Reduce the Risk of Neural Tube Defects*

Source	Population	Recommendation	Notes
CDC [64]	Women who are capable of becoming pregnant	400 mcg/day folic acid from dietary supplements and/or fortified foods	N/A
	Women who are planning a pregnancy and who had a previous pregnancy affected by an NTD	4,000 mcg/day folic acid starting 1 month before conception and continuing through the first 3 months of pregnancy	N/A
DGA 2020–2025 [17]	Women who are planning a pregnancy or who are capable of becoming pregnant	A daily supplement that contains 400–800 mcg folic acid, starting at least 1 month before conception and continuing through the first 2–3 months of pregnancy	N/A
ACOG [68]	Women who are planning a pregnancy or who are capable of becoming pregnant	400 mcg/day folic acid supplementation starting at least 1 month before conception and continuing through the first 12 weeks of pregnancy	N/A
	Women who had a previous pregnancy affected by an NTD or who have a family history of NTDs or a partner with a family history of NTDs	4,000 mcg/day folic acid supplementation, starting 3 months before conception and continuing through the first 12 weeks of pregnancy	N/A
USPSTF [67] and the American Academy of Family Physicians [69]	Women and adolescents who are planning a pregnancy or who are capable of becoming pregnant	A daily supplement that contains 400–800 mcg folic acid, starting at least 1 month before conception and continuing through the first 2–3 months of pregnancy	This recommendation does not apply to anyone who has previously given birth to an infant with an NTD or who are at high risk of NTDs for other reasons, such as those who take medications that block the action of folic acid.
Academy of Nutrition and Dietetics [16]	Women and adolescents who are capable of becoming pregnant	400 mcg/day folic acid from fortified foods and/or dietary supplements	N/A
	Women who had a previous pregnancy affected by an NTD	Consult with a health care provider regarding taking 4,000 mcg/day folic acid before and during the first trimester of pregnancy.	N/A
NICE [85]	Women who are capable of becoming pregnant and women in early pregnancy	400 mcg/day folic acid starting before conception and continuing through the first 12 weeks of pregnancy	N/A
	Women who had a previous pregnancy affected by an NTD or who have diabetes, a family history of NTDs, or a partner with a family history of NTDs	5,000 mcg/day folic acid starting before conception and continuing through the first 12 weeks of pregnancy	N/A
WHO [86,87]	Women who are planning a pregnancy and women in early pregnancy	400 mcg/day folic acid starting as early as possible, ideally 2 months before conception, and continuing through the first 12 weeks of pregnancy	Folic acid in combination with iron also helps improve other maternal and neonatal outcomes, including maternal anemia.
* Several other national and international expert groups, including the American Academy of Pediatrics [70], the Food and Nutrition Board of the National Academies of Sciences, Engineering, and Medicine [6], the American College of Medical Genetics and Genomics [88], the Canadian Institutes of Health Research [89], and the Society of Obstetricians and Gynaecologists of Canada [90] have issued similar recommendations.
Key:  ACOG = The American College of Obstetricians and Gynecologists CDC = Centers for Disease Control and Prevention DGA = Dietary Guidelines for Americans N/A = not applicable NICE = National Institute for Health and Care Excellence NTD = neural tube defect USPSTF = U.S. Preventive Services Task Force WHO = World Health Organization

More information is available in the ODS folate fact sheet for health professionals.

Iodine

Overview

Iodine is an essential component of the thyroid hormones thyroxine (T4) and triiodothyronine (T3). Thyroid hormones regulate many important biochemical reactions, including protein synthesis and enzymatic activity, and are critical determinants of metabolic activity [8,91,92]. They are also required for proper fetal and infant skeletal and central nervous system development.

The RDA for iodine during pregnancy is 220 mcg [8]. This value is higher than the RDA for nonpregnant females, which is 150 mcg. The WHO, United Nations Children’s Fund, and the International Council for the Control of Iodine Deficiency Disorders recommend a slightly higher iodine intake of 250 mcg/day during pregnancy [93,94].

Iodine is present in seaweed, fish and other seafood, iodized salt, dairy products, and eggs [91,95,96]. In addition, some commercially prepared bread contains iodine if the manufacturer uses potassium iodate or calcium iodate as dough conditioners. The ingredients list on bread product labels will include these dough conditioners if they are present in the product. The salt contained in processed foods is almost always noniodized salt, so it does not provide iodine.

Iodine is available in many dietary supplements, including some, but not all, prenatal supplements [12,22]. According to a 2021 evaluation of 188 prenatal supplements on the U.S. market, 76% of these products included iodine, with a median amount of 150 mcg/serving [30]. Another evaluation of 214 products found that nonprescription prenatal supplements contained a mean of 164 mcg of iodine, while prescription products contained a mean of 150 mcg [11].

Some pregnant women in the United States do not obtain sufficient amounts of iodine from their diet, especially those who follow vegetarian or vegan diets or do not use iodized salt [96-98]. An analysis of 2017–2020 NHANES data found that pregnant women had a median daily intake of iodine from foods of 216 mcg [99]. Dietary supplements that contain iodine can help pregnant women reach the recommended intake of iodine. When total intakes, including dietary supplements, are considered, pregnant women have a median daily iodine intake of 235 mcg and 10.2% of them have an intake that is below the EAR [99].

Urinary iodine concentration (UIC) is a common measure of iodine status, and median UIC, from spot samples collected as part of a large survey, can be used to characterize the iodine status of populations [100,101]. A median UIC of 150 to 249 mcg/L in a population indicates adequate iodine nutrition during pregnancy, while values less than 150 mcg/L indicate insufficient iodine nutrition [93,100]. Based on UIC measurements, a substantial proportion of pregnant women in the United States are iodine insufficient [99,102]. An analysis of 2017–2020 NHANES data found that pregnant women had a median UIC of 131.4 mcg/L, and 63.2% were below the threshold for sufficiency of 150 mcg/L [99].

Pregnant women in the United States rarely get excessive amounts of iodine. The UL for iodine during pregnancy is 900 mcg/day for ages 14 to 18 years and 1,100 mcg/day for ages 19 to 50 years [4]. These values are the same as those for nonpregnant females. An analysis of 2001–2014 NHANES data found that 0% of pregnant women age 20 to 40 years exceed the iodine UL when total iodine intakes from foods and dietary supplements are considered [99].

Iodine and pregnancy

Obtaining the recommended amount of iodine during pregnancy is crucial for proper fetal development. Iodine deficiency, which results from inadequate thyroid hormone production due to insufficient iodine, has multiple adverse effects on growth and development; severe deficiency is the most common cause of preventable intellectual disability in the world [94,103,104]. Congenital hypothyroidism (formerly known as cretinism) is the most recognized effect of severe iodine deficiency during pregnancy. It is characterized by severe, irreversible mental impairment, stunting, deaf mutism, and other physical abnormalities [104]. Severe iodine deficiency is also associated with higher risks of stillbirth, miscarriage, congenital abnormalities, and perinatal mortality [91,104].

Although severe iodine deficiency disorders are uncommon in the United States, mild-to-moderate iodine insufficiency during pregnancy has been documented in this country and may subtly affect fetal development [102,105-107]. A meta-analysis of 6,180 mother-child pairs from three birth cohorts in the Netherlands, Spain, and the United Kingdom found that the verbal IQ of children at 1.5 to 8 years of age was lower if their mothers had lower iodine status in their first trimester of pregnancy [108]. Other research has found inconsistent associations between maternal UIC and/or dietary iodine intake and neurodevelopmental outcomes in the child [109].

Iodine deficiency may also cause delays in conception. A U.S. population-based prospective cohort study found that women with moderate to severe iodine deficiency were 46% less likely to become pregnant over each menstrual cycle compared to women with adequate iodine status [110]. In contrast, iodine deficiency has not been associated with the risk of preeclampsia, gestational diabetes, stillbirth, or pregnancy loss, such as miscarriage [111-114].

The use of iodized salt and iodine-containing supplements during pregnancy can help ensure proper iodine status, but the effects of iodine supplements during pregnancy on infant and child neurodevelopment are not well understood [115-117]. In addition, both low and high iodine intakes during pregnancy are associated with neurodevelopmental deficits in children [118-120]. This raises questions about the potential adverse effects of iodine supplementation in pregnant women with sufficient iodine status or mild-to-moderate iodine deficiency. Many scientists have called for more research in this area [120,121].

A 2020 systematic review and meta-analysis examined the available evidence on the effects of iodine supplementation during pregnancy on maternal and infant thyroid function and child cognition in settings with mild-to-moderate iodine deficiency [122]. The review included 10 RCTs, four non-RCT interventions, and 23 observational studies in pregnant women with mild-to-moderate iodine deficiency. It found the following:

• Iodine supplementation did not affect child cognitive, language, or motor scores based on limited data from one adequately powered RCT.
• Maternal iodine supplementation did not affect neurodevelopment and had inconsistent effects on motor development in the observational studies and non-RCT interventional studies.
• Iodine supplementation reduced maternal thyroglobulin concentrations in most of the studies but did not affect maternal or infant thyroid-stimulating hormone and free thyroxine.

A 2017 Cochrane Review included 14 trials that investigated the effects of iodine supplementation during the preconceptional, pregnancy, or postpartum periods on maternal and child outcomes [123]. The trials were conducted in Europe, Australia, Chile, Morocco, New Zealand, Papua New Guinea, Peru, Thailand, and Zaire and they administered iodine alone or in combination with other vitamins and minerals. All but one trial reported baseline iodine status, and measurements indicated that participants had insufficient iodine intake (e.g., median UIC below 150 mcg/L). The review found the following:

• Iodine supplements reduced the risk of postpartum maternal hyperthyroidism by 68%, although this evidence was judged to be low quality.
• Iodine supplements did not affect the risk of perinatal mortality, low birthweight, neonatal hypothyroidism/elevated thyroid stimulating hormone, or elevated neonatal thyroid peroxidase antibodies. However, the evidence supporting these findings was judged to be very low to low quality.

Iodine supplementation recommendations

Many professional societies and public health organizations recommend iodine supplementation during pregnancy. These recommendations are summarized in Table 6.

Table 6. Recommendations for Iodine Supplementation Before and During Pregnancy

Source	Population	Recommendation	Notes
American Thyroid Association [124]	Women who are pregnant or who are planning a pregnancy	150 mcg/day iodine supplementation as potassium iodide, ideally starting 3 months before conception	Women with dietary restrictions, especially those who follow vegan diets, may need additional supplementation.
American Academy of Pediatrics [125]	Women who are pregnant or who are planning a pregnancy	150 mcg/day iodine supplementation, in addition to using iodized salt	N/A
Endocrine Society [126]	Women who are pregnant or who could become pregnant	Prenatal supplements that provide 150–200 mcg/day iodine in the form of potassium iodide or iodate, ideally starting before conception	N/A
2020–2025 DGA [17]	Women who are pregnant and follow a vegetarian or vegan diet	Consult with a health care provider to determine whether supplementation with iodine is necessary	N/A
European Thyroid Association [127]	Women who are pregnant	Daily iodine intake of 250 mcg/day, not to exceed 500 mcg/day	Sufficient iodine intake is usually achieved by supplementing with 150 mcg/day iodine, ideally starting before conception.
Australia and New Zealand National Health and Medical Resources Council [128]	Women who are pregnant or who are planning a pregnancy	150 mcg/day iodine supplementation*	N/A
WHO [94]	All pregnant women	250 mcg/day iodine supplementation, but only in areas where salt iodization programs do not meet the iodine requirements of pregnant women	N/A
* Australia and New Zealand have mandated the use of iodized salt in commercial breads [129]. Some experts note that these two factors combined might increase the total iodine intake during pregnancy beyond the optimal range [118].
Key: DGA = Dietary Guidelines for Americans N/A = not applicable WHO = World Health Organization

More information is available in the ODS iodine fact sheet for health professionals.

Iron

Overview

Iron is a mineral that is an essential component of hemoglobin and myoglobin, both of which are critical for oxygen transfer in the body [130,131]. Iron is important for muscle metabolism, healthy connective tissue, physical growth, neurological development, cellular functioning, and hormone synthesis [131,132].

The RDA for iron during pregnancy is 27 mg [8]. This value is higher than the RDA of 15 mg for nonpregnant women age 14 to 18 years and 18 mg for nonpregnant women age 19 to 50 years.

Dietary iron has two forms: heme iron and nonheme iron, which has a lower bioavailability [130]. Dietary sources of heme iron include animal proteins, such as lean meat and seafood [17]. Good sources of nonheme iron include nuts; beans; vegetables, such as spinach; and fortified grain products. Vitamin C enhances the absorption of nonheme iron, whereas calcium can interfere with the absorption of iron [8,133]. For this reason, some experts recommend taking stand-alone calcium and iron supplements at different times of the day [134].

Iron is available in many dietary supplements [12]. This includes most prenatal supplements; according to a 2021 evaluation of 188 prenatal supplements on the U.S. market, 89% of these products included iron, with a median amount of 27 mg/serving [30]. Another evaluation of 214 products found that nonprescription prenatal supplements contained a mean of 27 mg of iron, while prescription products contained a mean of 28 mg [11]. Gummy formulations often contain no iron [25].

Most pregnant women in the United States do not obtain sufficient amounts of iron from their diet. An analysis of 2001–2014 NHANES data found that pregnant women age 20 to 40 years had a mean daily intake of 17.2 mg of iron from foods, and 83.8% of them were consuming less than the EAR for iron [18]. Dietary supplements that contain iron can help pregnant women reach the recommended intake of iron during pregnancy, especially those who follow a vegetarian or vegan diet [17]. When total intakes, including dietary supplements, are considered, the mean daily iron intake among pregnant women in the United States increases to 38.3 mg, and the percentage of women who do not meet the EAR decreases to 36.2% [18].

Some women in the United States who are pregnant might obtain too much iron. The UL for iron during pregnancy is 45 mg/day for ages 14 years and older, which is the same as that for nonpregnant women in the same age range [8]. When total iron intakes from foods and dietary supplements are considered, 27.9% of pregnant women age 20 to 40 years in the United States exceed the UL according to 2001–2014 NHANES data [18].

Iron and pregnancy

Obtaining the recommended amount of iron during pregnancy is critical for maternal health and proper fetal development. It is estimated that 10% to 16% of women in the United States have iron deficiency during pregnancy, and the prevalence is higher—about 25%—during the third trimester [17,135].

Iron deficiency during pregnancy increases the risk of anemia, maternal and infant mortality, preterm birth, low birthweight, and impaired cognitive and behavioral development [86,136]. WHO guidelines define iron deficiency during pregnancy as ferritin concentrations that are less than 15 mcg/L in the first trimester in otherwise healthy women and anemia as hemoglobin concentrations that are less than 10.5 to 11 g/dL, depending on trimester [137,138]. It is important to note, however, that ferritin is not a sensitive marker of iron deficiency because acute and chronic inflammation can increase ferritin concentrations [139]. Similarly, hemoglobin is not a sensitive nor specific measure of iron deficiency. Hemoglobin concentrations can be interpreted in conjunction with ferritin measurements to help identify iron deficiency anemia (IDA) [135].

RCTs have shown that iron supplementation can prevent IDA in pregnant women and some of the related adverse consequences in their infants [140-143]. In some of these studies, iron supplementation was combined with folic acid or other vitamins and minerals.

A 2024 Cochrane Review included 40 trials that examined the effects of stand-alone daily iron supplements during pregnancy [143]. The trials were conducted in many countries, including 27 trials conducted in Europe, 8 in the United States, 5 in Africa, and 3 in China. The doses of iron supplements that were used in the trials varied widely, but the most commonly used doses were 60 mg (17 trials) and 30 mg (6 trials). The authors found the following:

• Iron supplementation reduced the risk of maternal IDA at term by 59% based on a moderate certainty of evidence.
• Iron supplementation reduced the risk of maternal anemia by 70% and maternal iron deficiency at term by 49%, although these findings were based on a low certainty of evidence.
• Iron supplementation reduced the risk of low birthweight by 16% based on a moderate certainty of evidence.
• Iron supplementation did not significantly affect infant birthweight or the risk of preterm birth, neonatal death, or congenital anomalies (e.g., NTDs) based on a very low to moderate certainty of evidence.

Although iron supplementation in pregnant women with iron deficiency has proven benefits, the benefits and harms of routine iron supplementation during pregnancy in iron-replete women are uncertain [144,145]. For example, some studies have linked iron supplementation or high iron status in iron-replete pregnant women with an increased risk of gestational diabetes, preterm birth, and impaired fetal growth [145].

These findings suggest a U-shaped risk of adverse health effects with both iron deficiency and iron excess. They are also reflected in the different recommendations from expert groups for iron supplementation during pregnancy.

Iron supplementation recommendations

The recommendations from professional societies, government agencies, and public health organizations for iron supplementation during pregnancy are summarized in Table 7.

Table 7. Recommendations for Iron Supplementation During Pregnancy

Source	Population	Recommendation	Notes
ACOG [146]	All pregnant women	Low-dose iron supplementation (dose and form not specified), starting in the first trimester	Screen all pregnant women for anemia in the first trimester and again at 24–28 weeks gestation.
	Pregnant women with IDA	Iron supplementation (dose and form not specified) in addition to prenatal vitamins	N/A
USPSTF [147]	Asymptomatic pregnant women	N/A	There is insufficient evidence for both screening for iron deficiency and for routine iron supplementation during pregnancy. This recommendation does not apply to pregnant women who are severely malnourished, have symptoms of iron deficiency or IDA, or have conditions such as sickle cell disease or nutritional deficiencies that may increase iron needs.
WHO [86]	All pregnant women	30 to 60 mg/day iron supplementation (plus 400 mcg/day folic acid), with the higher dose in settings where anemia during pregnancy is a severe public health problem	A weekly dose of 120 mg iron (plus 2,800 mcg folic acid) may be used instead if daily supplementation causes unacceptable side effects and if the prevalence of anemia during pregnancy in a population is less than 20%.
	Pregnant women with anemia	120 mg/day iron supplementation (plus 400 mcg/day folic acid) until hemoglobin concentration rises to normal	N/A
International Federation of Gynecology and Obstetrics [148]	Pregnant women and reproductive-aged females	N/A	Test hemoglobin and iron status in all reproductive-aged females as early as possible during pregnancy, and again before the end of the second trimester. Oral iron is the first-line intervention, but it is not always tolerated or successful at treating IDA. If IDA is identified at the beginning of the third trimester, the use of intravenous iron should be considered.
2020–2025 DGA [17]	Women who are pregnant or planning a pregnancy	A supplement that contains iron (dose and form not specified) when recommended by an obstetrician or other health care provider	Iron is a nutrient of public health concern during pregnancy and may be of particular concern for women who follow a vegetarian or vegan dietary pattern because nonheme iron is less bioavailable than heme iron.
FNB [8]	All pregnant women	Iron supplementation (dose and form not specified)	N/A
Academy of Nutrition and Dietetics [16,149]	All pregnant women	Iron supplementation (dose and form not specified)	N/A
	Pregnant women who follow vegetarian or vegan diets	30 mg/day iron supplementation from a prenatal supplement, a separate iron supplement, or a combination of the two	N/A
Key: ACOG = The American College of Obstetricians and Gynecologists DGA = Dietary Guidelines for Americans IDA = iron deficiency anemia N/A = not applicable USPSTF = U.S. Preventive Services Task Force WHO = World Health Organization

More information is available in the ODS fact sheet on iron for health professionals.

Magnesium

Overview

Magnesium is a cofactor in more than 600 enzyme systems that regulate diverse biochemical reactions in the body, including protein synthesis, muscle and nerve function, blood glucose control, and blood pressure regulation [5,150-153]. Magnesium also contributes to the structural development of bone and is required for the activation of vitamin D and the synthesis of DNA, RNA, and the antioxidant glutathione [154,155].

The RDA for magnesium during pregnancy is 400 mg for ages 14 to 18 years, 350 mg for ages 19 to 30 years, and 360 mg for ages 31 to 50 years [5]. These values are higher than the RDAs for nonpregnant females age 14 to 18 years (360 mg), age 19 to 30 years (310 mg), and age 31 to 50 years (320 mg).

Compared with standard reference body weights, higher body weights may increase magnesium requirements, and some experts believe that the magnesium DRIs, including the RDAs, should be recalculated to be higher than the current values [156]. This warrants further research. However, like other essential micronutrients, the current DRIs during pregnancy and other life stages do not differ by body weight, and the DRIs for magnesium that were established in 1997 remain in place at this time [5].

Good sources of magnesium include some green leafy vegetables, such as spinach, as well as legumes, nuts, seeds, and whole grains [5,153].

Magnesium is available in many dietary supplements, including some, but not all, prenatal supplements [12]. The authors of a 2021 evaluation of 188 prenatal supplements on the U.S. market reported that 66% of these products included magnesium, with a median amount of 50 mg/serving [30].

Many people in the United States, including those who are pregnant, do not obtain sufficient amounts of magnesium. According to NHANES data from 2001–2014, pregnant women ages 20 to 40 years had a mean daily intake of 294 mg of magnesium from foods, and 53.3% of them were consuming less than the EAR for magnesium [18]. Dietary supplements that contain magnesium can help pregnant women reach the recommended intake of magnesium, but when total intakes, including dietary supplements, are considered, the mean daily magnesium intake among pregnant women in the United States is 314 mg and 47.5% of women still fall below the EAR [18]. According to data from the ECHO consortium, some pregnant women may be more likely than others to have total magnesium intakes from foods and supplements below the EAR. These include women who are age 14 to 30 years, Hispanic or non-Hispanic Black, overweight or obese, or have less than a high school education [19].

The UL for magnesium during pregnancy is 350 mg/day [4]. This value is the same as that for nonpregnant females, and it applies to supplemental magnesium only; magnesium found naturally in foods and beverages does not have a UL. Less than 0.5% of pregnant women age 20 to 40 years in the United States exceed the magnesium UL, according to 2001–2014 NHANES data [18].

Magnesium and pregnancy

Adequate magnesium status during pregnancy is important for fetal growth and development [157]. Studies have examined whether magnesium supplementation affects the risk of preeclampsia, gestational diabetes, preterm birth, small for gestational age, perinatal mortality, and leg cramps [158-162]. Findings from these studies have been mixed. However, results suggest that magnesium supplements might be beneficial in some cases.

A 2014 Cochrane Review included 10 RCTs of magnesium supplements during pregnancy in 9,090 women and their infants [161]. Trials were conducted in several countries including Austria, China, Hungary, Italy, the United States, and South Africa. Doses of magnesium varied from 55 to 600 mg/day, and supplementation was initiated at 6 weeks gestation or later and typically lasted until birth. The review found the following:

• Magnesium supplementation during pregnancy had no effect on perinatal mortality or on small for gestational age.
• Magnesium supplementation did not affect risk of preeclampsia.

A more recent meta-analysis of seven RCTs in 2,653 pregnant women [162] found the following:

• Magnesium supplementation reduced the risk of preeclampsia by 24% but did not affect the risk of severe preeclampsia.
• Subgroup analyses found that magnesium supplements reduced the risk of preeclampsia only in trials that included high-risk pregnancies, not in those that did not.

Another meta-analysis of six RCTs in 3,068 pregnant women found that magnesium supplementation reduced the risk of preterm birth by 42%. However, there was significant heterogeneity among studies [160].

Magnesium deficiency can cause leg cramps, but the authors of a 2015 Cochrane Review of four RCTs concluded that it is unclear whether magnesium supplements reduce the incidence of leg cramps during pregnancy [40].

Magnesium supplementation recommendations

Currently, there are no specific recommendations from professional societies, government agencies, or public health organizations for magnesium supplementation during pregnancy.

More information is available in the ODS magnesium health professional fact sheet.

Omega-3 Fatty Acids and Seafood

Overview

Omega-3 fatty acids include the essential fatty acid alpha-linolenic acid (ALA) and the long-chain fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA). The body uses long-chain omega-3s to produce lipid mediators, such as eicosanoids (e.g., prostaglandins, leukotrienes) and inflammation resolving mediators (e.g., resolvins). Long-chain omega-3s are also used to form structural components of cell membranes, such as phospholipids [2,17,163].

ALA is present only in plant foods, including walnuts, flax seed, and canola oil [164]. DHA and EPA are present in fish and other seafood. Fatty fish, such as salmon, sardines, and tuna, are particularly rich sources of long-chain omega-3s. Seafood contains varying levels of methylmercury, but numerous studies, including systematic reviews, show that the health benefits of consuming seafood during the prenatal period outweigh the potential risks [165-167]. Nevertheless, U.S. government agencies encourage women who are pregnant to choose varieties of seafood that are lower in mercury, such as salmon, anchovies, sardines, Pacific oysters, and trout [17,168].

The AI for ALA during pregnancy is 1.4 g [2]. This value is higher than the AI of 1.1 g for nonpregnant females age 14 to 50 years.

Recommended intakes for long-chain omega-3s during pregnancy have not been established, but many expert groups recommend consuming 8 to 12 ounces of seafood per week, which would provide approximately 250 mg/day of DHA plus EPA [17,168,169]. Most women who are pregnant do not meet this recommendation [170]. According to an analysis of 2001–2014 NHANES data, the mean intake of seafood among pregnant women age 15 to 44 years is 0.44 ounces per day, or about 3 ounces per week [171]. The same analysis found that pregnant women age 20 to 40 years have an average daily DHA intake of 60.3 mg from food and 76.7 mg from food and supplements. When combined with EPA, the total average daily intake of DHA plus EPA from food is 78.7 mg and the average daily intake from food and supplements is 97.7 mg. Pregnant women who are Black are more likely than others to have low DHA intakes [172].

Long-chain omega-3s from marine (e.g., fish oil) or vegetarian (i.e., algal) sources are present in some dietary supplements. These products can help pregnant women obtain recommended amounts of long-chain omega-3s, especially those who do not eat seafood. However, omega-3s are not typically included in standard multivitamin/mineral supplements and only 35 to 39% of prescription and nonprescription prenatal supplements contain DHA [11,12,173]. Among prenatal supplements that do contain omega-3s, the average level of DHA is 368 mg in U.S. products and 404 mg in Canadian products, according to a 2024 evaluation of 68 prenatal supplements [174].

Omega-3s do not have a UL, although ALA has an acceptable macronutrient distribution range of 0.6% to 1.2% of energy for adults and children age 1 year and older [2]. The authors of a 2024 clinical practice guideline state that intakes up to 1,000 mg/day of DHA or DHA and EPA do not raise safety concerns in women who are pregnant [169].

Omega-3 fatty acids, seafood, and pregnancy

Obtaining sufficient amounts of long-chain omega-3s, particularly DHA, during pregnancy is important for maternal health and fetal growth and development. DHA is concentrated in the brain and the retina and accumulates most rapidly during the third trimester of pregnancy [2,175]. Many observational studies link higher maternal intakes of fish and other seafood with improved child health outcomes [170,176-178]. One systematic review included 29 prospective cohort studies in 102,944 healthy mother-offspring pairs [167]. The studies were conducted in the United States, Europe, the United Kingdom, Asia, and Africa, and the authors found the following:

• Maternal seafood consumption of 4 ounces/week was associated with improved neurocognitive development, and these improvements continued with intakes of more than 12 ounces/week.
• No net adverse neurocognitive outcomes were reported at the highest ranges of maternal seafood intakes (30 ounces/week or more) despite the associated increases in mercury exposure.

Results from RCTs have not shown consistent benefits from maternal supplementation with EPA and/or DHA during pregnancy on infant cognition or visual development [175,179]. However, long-chain omega-3 supplements, particularly DHA, have been shown to reduce the risk of preterm and early preterm birth [169,180].

A 2018 Cochrane Review assessed the effects of long-chain omega-3s from supplements and/or foods during pregnancy on maternal and neonatal outcomes in 19,927 women [181]. It included 70 RCTs, that were conducted in multiple countries, including 16 trials in the United States, 8 in Iran, 6 in the United Kingdom, and 4 in the Netherlands. Fifty of the trials administered supplements that contained only omega-3s, while the remainder administered omega-3s as food or combination products. Based on a high quality of evidence, the authors concluded the following:

• Long-chain omega-3s reduced the risk of preterm birth (birth at <37 weeks) by 11%, and the risk of early preterm birth (birth at <34 weeks) by 42%.
• Long-chain omega-3s also reduced the risk of low birthweight.

A 2022 statement from the International Society for the Study of Fatty Acids and Lipids that included two large trials that were published after the Cochrane Review confirmed these findings, showing a 12% reduction in the risk of preterm birth and a 35% reduction in the risk of early preterm birth among those taking long-chain omega-3 supplements [182].

A 2016 Agency for Healthcare Research and Quality (AHRQ) report evaluated the results of 95 RCTs and 48 prospective, longitudinal studies, and case-control studies from around the world [183]. It found that long-chain omega-3 supplementation during pregnancy slightly increased gestational length and birth weight compared with placebo but had no consistent effects on other maternal and child health outcomes.

In addition, some, but not all, RCTs have found that maternal supplementation with EPA and/or DHA during pregnancy improves immune function and reduces the incidence of severe atopic dermatitis, food sensitivities, and/or asthma in the child [163]. However, more research is needed to confirm these findings.

Despite these potential health benefits, many pregnant women do not meet the recommended seafood intake of 8 to 12 ounces per week [170]. Thus, they likely have intakes of long-chain omega-3s that do not meet recommended amounts. In addition to long-chain omega-3s, seafood provides other essential nutrients including vitamin D, calcium, potassium, iron, choline, iodine, and magnesium.

Seafood and omega-3 supplementation recommendations

Several professional societies, government agencies, and public health organizations recommend seafood consumption during pregnancy, and some recommend additional DHA and/or EPA intake. These recommendations are summarized in Table 8.

Table 8. Recommendations for Seafood, Docosahexaenoic Acid, and Eicosapentaenoic Acid Supplementation During Pregnancy

Source	Population	Recommendation	Notes
ACOG [15]	All pregnant women	Consume 8–12 ounces/week of seafood that is lower in mercury.*	N/A
FDA [168]	All pregnant women	Consume 8–12 ounces/week of seafood that is lower in mercury.*	N/A
2020–2025 DGA [17]	All pregnant women	Consume 8–12 ounces/week of seafood that is lower in mercury.*	Seafood consumption is associated with favorable measures of cognitive development in young children.
	Pregnant women who follow vegetarian or vegan diets	Consult with a health care provider to determine whether supplementation with EPA/DHA is necessary.
EFSA [184]	All pregnant women	Consume an additional 100–200 mg/day DHA during pregnancy on top of 250 mg/day of DHA plus EPA for all adults.	N/A
Food and Agriculture Organization of the United Nations [185]	All pregnant women	Consume at least 300 mg/day DHA plus EPA, of which 200 mg is DHA.	N/A
Clinical practice guideline from the American Journal of Obstetrics & Gynecology Maternal-Fetal Medicine [169]	All women of childbearing age and pregnant women	Consume at least 250 mg/day DHA plus EPA from diet or supplements, and an additional 100–200 mg/day of DHA during pregnancy.	The purpose of this recommendation is to reduce the risk of preterm and early preterm birth.
	Pregnant women with low DHA intake (<150 mg DHA/day) and/or status**	Consume 600–1000 mg/day DHA plus EPA or DHA alone, beginning in the second trimester (no later than 20 weeks gestation).
* The FDA has a list of seafood choices that are lower in mercury, including salmon, sardines, oysters, and trout.
** A validated tool consisting of seven questions is available to help clinicians estimate the DHA intake of pregnant women in the United States [186].
Key: ACOG = The American College of Obstetricians and Gynecologists DGA = Dietary Guidelines for Americans DHA = docosahexaenoic acid EFSA = The European Food Safety Authority EPA = eicosapentaenoic acid FDA = Food and Drug Administration N/A = not applicable

More information is available in the ODS omega-3 fatty acids fact sheet for health professionals.

Vitamin A

Overview

Vitamin A refers to a group of fat-soluble compounds [187,188]. It has two main forms: preformed vitamin A (retinol and retinyl esters) and provitamin A carotenoids, including beta-carotene, alpha-carotene, and beta-cryptoxanthin. The body can convert provitamin A carotenoids into vitamin A.

Vitamin A is involved in immune function; cellular communication; growth and development; male and female reproduction; and the formation and maintenance of the heart, lungs, eyes, and other organs. It is particularly important for vision [7,187-189].

The unit of measurement for vitamin A is mcg retinol activity equivalents (RAE) to account for the different bioactivities of retinol and provitamin A carotenoids, but International Units (IUs) were previously used [60]. Conversions from IU to mcg RAE are as follows [190-192]:

• 1 IU retinol = 0.3 mcg RAE
• 1 IU supplemental beta-carotene = 0.3 mcg RAE
• 1 IU dietary beta-carotene = 0.05 mcg RAE
• 1 IU dietary alpha-carotene or beta-cryptoxanthin = 0.025 mcg RAE

The RDA for vitamin A during pregnancy is 750 mcg RAE for ages 14 to18 years and 770 mcg RAE for ages 19 to 50 years [8]. These values are higher than the RDA for nonpregnant females of 700 mcg day for ages 14 and older.

Animal products, such as dairy, eggs, fish, and organ meats, are good dietary sources of preformed vitamin A. Provitamin A carotenoids are present in plant foods including leafy green vegetables, orange and yellow vegetables, tomatoes, fruits, and some vegetable oils [8,187,193]. Vitamin A is routinely added as a fortificant to some foods, including milk and margarine [187,188].

Vitamin A is available in many dietary supplements, including many prenatal supplements [12]. A 2022 evaluation of 188 prenatal supplements on the U.S. market found that 73% of prenatal supplements included beta-carotene, with a median amount of 3,040 IU/serving [23]. The same evaluation found that 35% of prenatal supplements included preformed vitamin A, with a median amount of 2,487 IU/serving.

Frank vitamin A deficiency is rare in the United States, but some women who are pregnant do not obtain sufficient amounts of vitamin A from their diet [187]. An analysis of 2001–2014 NHANES data found that pregnant women age 20 to 40 had a mean dietary vitamin A intake of 696 mcg/day, and 27.7% of them were consuming less than the EAR for vitamin A [18]. Dietary supplements that contain vitamin A can help pregnant women reach the recommended intake of vitamin A. When dietary supplement intakes are included, the mean daily vitamin A intake among pregnant women in the United States increases to 1,283 mcg and the percentage of women who fall below the EAR decreases to 15.5% [18].

The UL for preformed vitamin A during pregnancy is 2,800 mcg/day for ages 14 to 18 years and 3,000 mcg/day for ages 19 to 50 years [8]. These values are the same as those for nonpregnant females. Beta-carotene and other provitamin A carotenoids do not have a UL.

Excessive intakes of preformed vitamin A during pregnancy can cause congenital birth defects, including malformations of the eye, skull, lungs, and heart [187,193]. Therefore, women who are or who might be pregnant should not take high doses of supplements that contain preformed vitamin A and should be aware that some prescription medications contain synthetic retinoids derived from vitamin A. Beta-carotene and other provitamin A carotenoids, however, are not known to cause reproductive toxicity [187].

Less than 0.5% of pregnant women age 20 to 40 years in the United States have total intakes that exceed the UL for preformed vitamin A, according to 2001–2014 NHANES data [18].

Vitamin A and pregnancy

Obtaining the recommended amount of vitamin A during pregnancy is important for both fetal and maternal health. Several studies have examined whether supplemental vitamin A affects pregnancy outcomes such as preterm birth and low birthweight, but results from these studies have been inconsistent.

A 2023 meta-analysis included 55 studies that evaluated perinatal growth outcomes in a total of 426,098 pregnancies in low-, middle-, and high-income countries around the world [194]. These studies evaluated the effects of vitamin A supplements alone; in combination with other micronutrients; or with other interventions, including dietary patterns that were rich in vitamin A. The analysis found the following:

• Vitamin A decreased the risk of preterm birth by 19% and the risk of low birthweight by 16%.
• In RCTs that administered vitamin A supplementation alone:
  • The risk of preterm birth was reduced by 9% in healthy mothers but not in mothers with health complications, such as those with HIV or night blindness.
  • The risk of low birthweight was reduced by 24% in mothers with health complications but not in healthy mothers.
• Vitamin A did not affect the risk of neonatal birth defects.

A 2015 Cochrane Review also evaluated vitamin A supplementation during pregnancy and included 19 trials in more than 310,00 pregnant women in low-, middle-, and high-income countries [195]. The review found the following:

• Vitamin A supplementation did not affect the risk of maternal mortality, perinatal mortality, neonatal mortality, stillbirth, neonatal anemia, preterm birth, or low birthweight.
• Vitamin A supplementation reduced the risk of maternal night blindness and anemia. It also reduced the risk of maternal clinical infection, but the quality of this evidence was judged to be low.

The authors concluded that vitamin A supplementation during pregnancy reduces the risk of anemia and night blindness in women who live in areas where vitamin A deficiency is common or in those with HIV.

Vitamin A supplementation recommendations

As summarized in Table 9, WHO recommends vitamin A supplementation only in certain circumstances to prevent night blindness [196]. Currently, there are no other recommendations from professional societies, government agencies, or public health organizations for vitamin A supplementation during pregnancy.

Table 9. Recommendations for Vitamin A Supplementation During Pregnancy to Prevent Night Blindness

Source	Population	Recommendation	Notes
WHO [196]	Pregnant women living in areas where vitamin A deficiency is a severe public health problem	Vitamin A supplementation (dose and form not specified) to prevent night blindness	N/A
Key: N/A = not applicable WHO = World Health Organization

More information is available in the ODS fact sheet on vitamin A for health professionals.

Vitamin B6

Overview

Vitamin B6 (also called pyridoxine) is the generic name for six compounds with vitamin B6 activity that the body converts to the coenzyme pyridoxal 5’-phosphate (PLP). Through PLP, vitamin B6 is involved with almost all aspects of metabolism and cellular homeostasis, including protein metabolism, one-carbon metabolism, gluconeogenesis, glycogenolysis, and hemoglobin formation [6,197]. PLP is also required for neurotransmitter metabolism, which is important for cognitive development.

The RDA for vitamin B6 during pregnancy is 1.9 mg [6]. This value is higher than the RDA of 1.2 mg for nonpregnant females age 14 to 18 years and the RDA of 1.3 mg for those age 19 to 50 years.

Good sources of vitamin B6 include fish, beef, poultry, organ meats, and potatoes and other starchy vegetables [6,197]. Some noncitrus fruits, such as bananas, raisins, and watermelon, also contain vitamin B6.

Vitamin B6 is available in many dietary supplements [12]. This includes almost all prenatal supplements; a 2022 evaluation of 188 prenatal supplements on the U.S. market found that 97% of these products included vitamin B6, with a median amount of 5 mg/serving [23].

Some pregnant women in the United States do not obtain sufficient amounts of vitamin B6. According to NHANES data from 2001–2014, pregnant women age 20 to 40 years had a mean daily intake of vitamin B6 from foods of 2.1 mg, and 25.4% of them were consuming less than the EAR for vitamin B6 [18]. Dietary supplements that contain vitamin B6 can help pregnant women reach the recommended amounts. When total intakes, including dietary supplements, are considered, the mean daily vitamin B6 intake among pregnant women in the United States increases to 7.8 mg, and the percentage of women who fall below the EAR decreases to 11.5% [18].

The UL for vitamin B6 during pregnancy is 100 mg/day [4]. This is the same as the value for nonpregnant females age 14 to 50 years. The UL is virtually impossible to reach from food intake alone. Although some dietary supplements contain high doses of vitamin B6 [12], 2001–2014 NHANES data indicate that less than 0.5% of pregnant women age 20 to 40 years in the United States have total vitamin B6 intakes from foods and dietary supplements that exceed the UL [18].

The Panel on Nutrition, Novel Foods and Food Allergens of the European Food Safety Authority (EFSA) has set an upper limit for vitamin B6 of 12 mg/day for all adults, including those who are pregnant [198]. This value is substantially lower than the 100 mg/day UL set by the FNB [6].

Vitamin B6 and pregnancy

Adequate vitamin B6 status during pregnancy is important for proper nervous system development and function, and a deficiency might increase the risk of preterm birth and preeclampsia [23,86]. Most studies that have evaluated the use of vitamin B6 supplementation during pregnancy have focused on alleviating nausea and vomiting, but some studies have evaluated other outcomes.

A 2015 Cochrane Review evaluated the use of vitamin B6, among other interventions, to alleviate nausea and vomiting during early pregnancy [199]. The review included only two clinical trials, one conducted in the United States [200] and the other in Thailand [201], that compared the use of vitamin B6 with placebo. These trials found that 30 to 75 mg of vitamin B6 per day decreased nausea in pregnant women. However, the Cochrane Review authors concluded that there was only limited evidence to support the use of vitamin B6 for this purpose [199].

Vitamin B6 has also been studied in combination with doxylamine (an antihistamine). Clinical trials have found that this combination reduces nausea and vomiting during pregnancy by 70% [202,203].

A 2015 Cochrane Review examined the effects of vitamin B6 supplements on pregnancy outcomes other than nausea and vomiting [204]. The review included four RCTs that evaluated the use of vitamin B6 supplements during pregnancy in 1,646 women. In three of the trials, the doses of vitamin B6 ranged from 2.6 to 25 mg/day and supplementation was initiated at various gestational ages until delivery. In the fourth trial, a single dose of 100 mg was administered 2 to 10 hours before birth. The authors of the review reported that vitamin B6 supplementation did not affect the risk of eclampsia or preeclampsia, although this finding was based on a low quality of evidence.

Vitamin B6 supplementation recommendations

A couple of professional societies and public health organizations recommend vitamin B6 supplementation during pregnancy to alleviate nausea and vomiting. These recommendations are summarized in Table 10.

Table 10. Recommendations for Vitamin B6 Supplementation During Pregnancy to Alleviate Nausea and Vomiting

Source	Population	Recommendation	Notes
ACOG [205]	All pregnant women	Vitamin B6 supplementation (dose and form not specified) alone or in combination with doxylamine is a safe and effective treatment for alleviating nausea and vomiting during pregnancy and should be considered as a first-line treatment.	This recommendation is based on good and consistent scientific evidence. Clinical trials have used 10–25 mg of pyridoxine every 8 hours.*
WHO [86]	All pregnant women	Vitamin B6 supplementation (dose and form not specified) can relieve nausea in early pregnancy.	Vitamin B6 supplementation during pregnancy is not recommended to improve maternal and perinatal outcomes.
* These doses approach the UL for vitamin B6 during pregnancy of 100 mg/day [6].
Key: ACOG = The American College of Obstetricians and Gynecologists UL = tolerable upper intake level WHO = World Health Organization

More information is available in the ODS vitamin B6 fact sheet for health professionals.

Vitamin B12

Overview

Vitamin B12 is a water-soluble vitamin that is required for central nervous system function, healthy red blood cell formation, and the synthesis of DNA and RNA [6,206,207]. It contains the mineral cobalt, so compounds that have vitamin B12 activity are collectively called cobalamins.

The RDA for vitamin B12 during pregnancy is 2.6 mcg [6]. This is higher than the RDA of 2.4 mcg for nonpregnant females age 14 years and older.

Vitamin B12 is present in animal foods, including fish, meat, poultry, eggs, and dairy products [207-209]. Plant foods do not naturally contain vitamin B12. However, some foods, such as plant-based milk substitutes, breakfast cereals, and nutritional yeasts, are fortified with vitamin B12.

Vitamin B12 is available in many dietary supplements [12]. This includes almost all prenatal supplements; a 2022 evaluation of 188 prenatal supplements on the U.S. market found that 97% of these products included vitamin B12, with a median amount of 8.5 mcg/serving [23].

Most pregnant women in the United States obtain sufficient amounts of vitamin B12. An analysis of 2001–2014 NHANES data found that the average daily vitamin B12 intake from foods alone in pregnant women was 5.6 mcg, and only 2.4% of these women did not meet the EAR for vitamin B12 [18]. However, because vitamin B12 is present only in animal products and some fortified foods, pregnant women who follow a vegetarian or vegan diet have an increased risk of inadequate vitamin B12 intakes [210]. Consuming foods that are fortified with vitamin B12 and vitamin B12 supplements can substantially reduce the risk of deficiency. When total intakes, including dietary supplements, are considered, the mean daily vitamin B12 intake among pregnant women in the United States increases to 19.2 mcg and the percentage of women who fall below the EAR decreases to 1.4% [18].

Certain conditions, such as pernicious anemia and achlorhydria, cause malabsorption of vitamin B12. Malabsorption can also occur in people who take proton pump inhibitors. This can result in vitamin B12 deficiency despite adequate oral intakes [207,211]. Pernicious anemia is usually treated with intramuscular vitamin B12 injections to bypass any barriers to absorption.

Vitamin B12 does not have a UL for any age group [6].

Vitamin B12 and pregnancy

Vitamin B12 deficiency during pregnancy can cause maternal and infant anemia and might increase the risk of NTDs, failure to thrive, spontaneous abortion, low birthweight, and developmental delays [211-216]. In addition, pregnant women with preeclampsia have been found to have lower vitamin B12 concentrations than those who are normotensive [217]. Vitamin B12 intake during pregnancy also affects fetal vitamin B12 stores because these develop in utero [10].

Despite the importance of vitamin B12 during pregnancy, research on the effects of vitamin B12 supplementation on maternal and infant health outcomes is limited [216,218].

A 2024 Cochrane Review included five trials that evaluated the effects of vitamin B12 supplementation in 984 pregnant women in India, Bangladesh, South Africa, and Croatia [216]. Twenty-six percent to 51% of these women were vitamin B12 deficient. The authors concluded that vitamin B12 supplements:

• May improve B12 status during pregnancy and postpartum, but the certainty of this evidence was very low.
• Appear to improve infant vitamin B12 status.
• Have uncertain effects on clinical or functional health outcomes, including preterm birth and low birthweight.

Vitamin B12 supplementation recommendations

Table 11 summarizes recommendations from the 2020–2025 DGA and the Academy of Nutrition and Dietetics for vitamin B12 supplementation during pregnancy for women who follow vegetarian or vegan diets. Other experts also recommend vitamin B12 supplementation during pregnancy for women with known vitamin B12 deficiency or those who are at high risk of deficiency, such as those who follow vegan or vegetarian diets [211,212].

Table 11. Recommendations for Vitamin B12 Supplementation During Pregnancy

Source	Population	Recommendation	Notes
2020–2025 DGA [17]	Pregnant women who follow vegetarian or vegan diets	Consult with a health care provider to determine whether supplementation with vitamin B12 is necessary.	N/A
The Academy of Nutrition and Dietetics [149]	Pregnant women who follow vegetarian or vegan diets	Vitamin B12 supplements or fortified foods, especially for women who follow vegan diets	N/A
Key: DGA = Dietary Guidelines for Americans N/A = not applicable

More information is available in the ODS fact sheet on vitamin B12 for health professionals.

Vitamin D

Overview

Vitamin D, also known as calciferol, is a fat-soluble vitamin that exists in two main forms: vitamin D2 and vitamin D3. Because vitamin D promotes calcium absorption and enables normal bone mineralization, it is important for bone health. It also plays a role in inflammation, cell growth, neuromuscular and immune function, and glucose metabolism [4,219-221].

The current unit of measurement for vitamin D is mcg, but IUs were used in the past; 1 mcg vitamin D is equal to 40 IU [191]. The RDA for vitamin D during pregnancy is 15 mcg (600 IU) [4]. This is the same as the value for nonpregnant females age 14 to 50 years.

The main dietary sources of vitamin D are the flesh of fatty fish (trout, salmon, tuna, and mackerel) and fish liver oils. Beef liver, egg yolks, and cheese have small amounts of vitamin D. Almost all of the U.S. milk supply is fortified with vitamin D, and some plant-based milk substitutes are also fortified with vitamin D [4,219]. People in the United States get most of their vitamin D from fortified foods [4,222]. The body also makes vitamin D from sun exposure, and most people meet at least some of their vitamin D needs through this means [4].

Vitamin D is available in many dietary supplements [12]. This includes almost all prenatal supplements; a 2022 evaluation of 188 prenatal supplements on the U.S. market found that 98% of these products included vitamin D, with a median amount of 550 IU (13.8 mcg)/serving [23]. Another evaluation of 214 products found that nonprescription prenatal supplements contained a mean of 646 IU (16.2 mcg), while prescription products contained a mean of 462 IU (11.6 mcg) [11].

According to the 2020–2025 DGA, vitamin D is a nutrient of public health concern because it is underconsumed by the U.S. population [17]. Similarly, most pregnant women in the United States consume less than the recommended amounts of vitamin D. An analysis of 2001–2014 NHANES data found that pregnant women age 20 to 40 years had a mean daily intake of vitamin D from foods of 5.5 mcg, and 92.1% of them were consuming less than the EAR for vitamin D [18].

Dietary supplements that contain vitamin D can help pregnant women reach the recommended intake of vitamin D and may be particularly useful for those who follow a vegan diet. However, many pregnant women still fall short. When total intakes, including dietary supplements, are considered, the mean daily intake of vitamin D in pregnant women in the United States increases to 11.3 mcg, and 46.4% of women fall below the EAR [18].

The UL for vitamin D during pregnancy is 100 mcg/day [4]. This is the same as the value for nonpregnant females age 14 to 50 years. Less than 0.5% of pregnant women age 20 to 40 years in the United States have total vitamin D intakes from foods and dietary supplements that exceed the UL, according to 2001–2014 NHANES data [18].

Vitamin D and pregnancy

Vitamin D is crucial during pregnancy for proper fetal development, including for bone growth. Vitamin D deficiency has been associated with several adverse pregnancy outcomes including congenital rickets and an increased risk of preeclampsia, gestational diabetes, and preterm birth [223-225]. However, the effects of vitamin D supplementation on pregnancy outcomes are mixed [223].

A 2024 Cochrane Review included 10 trials in 3,867 women from Australia, Bangladesh, Brazil, India, Iran, New Zealand, Pakistan, and the United Kingdom that evaluated the effects of vitamin D supplements alone or in combination with other micronutrients during pregnancy [223]. It found the following:

• Vitamin D supplementation alone reduced the risk of severe postpartum hemorrhage, but this was based on a low certainty of evidence.
• Vitamin D supplementation alone, vitamin D plus calcium, or vitamin D plus calcium and other vitamins and minerals did not reduce the risk of preeclampsia, gestational diabetes, low birthweight, preterm birth, nephritic syndrome, or other adverse health outcomes, but these findings were based on low or very low certainty of evidence.

A systematic review and meta-analysis of 20 RCTs that included 1,682 pregnant women with gestational diabetes found that vitamin D supplementation improved maternal blood lipid concentrations and decreased the risk of preterm birth by 63%, the risk of hyperbilirubinemia by 62%, and the risk of neonatal hospitalization by 62% [226]. A meta-analysis of three RCTs found increased bone mineral density among children born to women who took vitamin D supplements during their pregnancies, but the authors call for further research to confirm these findings [227]. Another meta-analysis of four RCTs in 3,931 pregnant women found that vitamin D supplementation during pregnancy did not affect the risk of congenital abnormalities in their children, such as congenital heart disease or NTDs [228].

Vitamin D supplementation recommendations

The recommendations from professional societies, government agencies, and public health organizations on vitamin D supplementation during pregnancy differ somewhat. These recommendations are summarized in Table 12.

Table 12. Recommendations for Vitamin D Supplementation During Pregnancy

Source	Population	Recommendation	Notes
ACOG [225]	All pregnant women	N/A	There is insufficient evidence to recommend screening all pregnant women for vitamin D deficiency or to recommend routine vitamin D supplementation beyond what is included in a prenatal supplement. There is also insufficient evidence to recommend vitamin D supplementation to prevent preterm birth or preeclampsia. Most experts agree that 25–50 mcg/day (1,000–2,000 IU) vitamin D is safe for pregnant women with vitamin D deficiency.
Endocrine Society [229,230]	All pregnant women	Vitamin D supplementation (dose and form not specified)	Vitamin D may lower the risk of preeclampsia, intrauterine and neonatal mortality, preterm birth, and small for gestational age.
2020–2025 DGA [17]	All pregnant women	N/A	Vitamin D is a nutrient of public health concern because it is underconsumed by the U.S. population, including pregnant women.
United Kingdom Health Departments and NICE [231,232]	All pregnant women	Daily supplement that contains 10 mcg vitamin D	The purpose of this recommendation is to ensure that maternal vitamin D needs are met and to build fetal vitamin D stores.
WHO [233]	All pregnant women	Does not recommend vitamin D supplements for all pregnant women to improve maternal and perinatal outcomes	N/A
	Pregnant women with suspected vitamin D deficiency	Vitamin D supplementation may be given at a dose of 5 mcg/day	This recommendation may also apply to women in populations with limited sun exposure.
Key: ACOG = The American College of Obstetricians and Gynecologists DGA = Dietary Guidelines for Americans N/A = not applicable NICE = National Institute for Health and Care Excellence RDA = Recommended Dietary Allowance WHO = World Health Organization

More information is available in the ODS fact sheet on vitamin D for health professionals.

Zinc

Overview

Zinc is involved in many aspects of cellular metabolism. It is required for the catalytic activity of hundreds of enzymes, and it plays a role in enhancing immune function, protein and DNA synthesis, wound healing, and cell signaling and division [8,234-236]. Zinc also supports healthy growth and development of the fetus during pregnancy [234,235,237].

The RDA for zinc during pregnancy is 12 mg for ages 14 to 18 years and 11 mg for ages 19 to 50 [8]. These values are higher than those for nonpregnant females of 9 mg for ages 14 to 18 years and 8 mg for ages 31 to 50 years.

Good sources of zinc include meat, fish, and seafood, especially oysters [235]. Dairy products and eggs also contain zinc. Beans, nuts, and whole grains contain zinc, but the bioavailability of zinc from these foods is lower than that from animal foods because these plant foods contain phytates that inhibit zinc absorption [238].

Zinc is available in many dietary supplements [12]. This includes most prenatal supplements; the authors of a 2021 evaluation of 188 prenatal supplements on the U.S. market reported that 89% of these products included zinc with a median amount of 15 mg/serving [30].

Zinc deficiency is common in low- and middle-income countries [234]. Most people in the United States consume adequate amounts of zinc, but some, including those who are pregnant, might have marginal intakes. People who follow vegetarian or vegan diets are particularly likely to have low zinc status [239]. According to 2001–2014 NHANES data, pregnant women age 20 to 40 years had a mean daily intake of 12.4 mg of zinc from foods, and 21.5% of them were consuming less than the EAR for zinc [18].

Dietary supplements that contain zinc can help pregnant women reach recommended amounts, especially those who follow a vegetarian or vegan diet. When total intakes, including dietary supplements, are considered, the mean daily zinc intake among pregnant women in the United States increases to 22.7 mg and the percentage of women who fall below the EAR decreases to 10.9% [18].

The UL for zinc during pregnancy is 34 mg/day for ages 14 to 18 years and 40 mg for ages 19 to 50 years [8]. These values are the same as those for nonpregnant females. When total zinc intakes from foods and dietary supplements are considered, 7.1% of pregnant women age 20 to 40 years in the United States exceed the zinc UL, according to 2001–2014 NHANES data [18].

Zinc and pregnancy

Adequate zinc status during pregnancy is important for fetal growth and development. Low serum zinc concentrations during pregnancy might increase the risk of gestational hypertension, low birthweight, and preterm birth [240-242]. However, the effects of zinc supplementation on pregnancy outcomes are unclear.

A 2020 systematic review and meta-analysis included 13 studies that evaluated zinc supplementation during pregnancy in low- and middle-income countries [243]. The authors concluded that zinc supplementation may increase maternal serum zinc concentrations, but it does not affect the risk of preeclampsia or eclampsia, preterm birth, low birthweight, or small for gestational age.

A 2021 Cochrane Review that included 25 RCTs in more than 18,000 women and their infants concluded that there is not enough evidence to determine whether zinc supplementation during pregnancy improves maternal or neonatal outcomes [242].

Zinc supplementation recommendations

The 2020–2025 DGA recommends that pregnant women who follow vegetarian or vegan diets consult with a health care provider to determine whether zinc supplementation is necessary [17].

WHO does not recommend zinc supplementation during pregnancy as part of routine care [244]. Currently, there are no other recommendations from professional societies, government agencies, or public health organizations for zinc supplementation during pregnancy.

More information is available in the ODS fact sheet on zinc for health professionals.

Botanical Ingredients

Botanical ingredients have been used in pregnancy for centuries. Some evidence supports the use of some botanicals during pregnancy, such as ginger for alleviating nausea [86,205,245], but most botanicals lack evidence of their safety and efficacy. This is due in part to limited research in pregnant women, given the delicate nature of this life stage. In addition, the high variability of botanical products in terms of their complexity, combination, and preparation complicates safety and efficacy assessments [246].

Because of potential safety concerns, caution is warranted when considering the use of any botanical supplement during pregnancy [247,248]. Nonetheless, 33% of nonprescription prenatal supplements and 6% of prescription prenatal supplements include a botanical ingredient [11]. For example, some prenatal supplements contain peppermint leaf or ginger root [12]. In addition, many pregnant women may be using botanical products without consulting with their health care providers [249].

Caffeine from Botanical Sources

Some botanicals, such as green tea, yerba mate, kola nut, and guarana, contain caffeine. Caffeine is a stimulant that crosses the placenta during pregnancy, and high caffeine doses could adversely affect fetal growth and other pregnancy outcomes [10,250]. In addition, pregnancy can affect caffeine clearance from the body, substantially increasing its half-life. However, experts do not believe that moderate caffeine intake during pregnancy is a concern for healthy women.

A 12-ounce cup of brewed coffee contains about 113 to 247 mg of caffeine, whereas green tea contains about 37 mg, and black tea contains about 71 mg [251]. Ascertaining the caffeine content of dietary supplements can be challenging because some supplements that contain botanical sources of caffeine do not declare the amount of caffeine on the product label.

ACOG states that moderate caffeine consumption during pregnancy (up to 200 mg/day) does not appear to increase the risk of miscarriage or preterm birth [252]. They note that whether caffeine increases the risk of intrauterine growth restriction is unclear.

Similarly, the 2020–2025 DGA states that low to moderate amounts of caffeine (up to about 300 mg/day) do not usually have adverse effects on the infant [17]. They add that women who are pregnant or who could be pregnant should consult their health care providers for advice about caffeine.

Other experts agree that caffeine intakes up to 200 to 300 mg/day appear to be safe during pregnancy [10,250,253,254].

German Chamomile (Matricaria chamomilla)

German chamomile is an herb that belongs to the Asteraceae family. Dietary supplements made from the dried flower of German chamomile are promoted for alleviating nausea and vomiting during pregnancy, but the evidence is very limited:

• A 2015 Cochrane Review evaluated the use of German chamomile, among other interventions, for alleviating nausea and vomiting during early pregnancy [199]. The review included only one study that compared the effects of German chamomile (500 mg of the dried flower) to ginger and placebo; each intervention was administered twice daily for 1 week in pregnant women with nausea and vomiting. Compared with placebo, German chamomile reduced nausea and vomiting. However, the Cochrane authors noted that there is not enough high-quality evidence to recommend using German chamomile during pregnancy.
• WHO recommends using chamomile to relieve nausea in early pregnancy, but they note that this recommendation is based on low-certainty evidence [86].

German chamomile, like other plants in the Asteraceae family, can cause allergic reactions, including anaphylaxis [255-257]. The safety of using German chamomile during pregnancy has not been well studied [258]. Another type of chamomile—Roman chamomile (Chameamelum nobile)—may cause spontaneous abortion, so experts advise against its use during pregnancy [258].

Ginger (Zingiber officinale)

Ginger rhizome (underground stem) is commonly used in foods and beverages. It is also available in dietary supplements, usually as powdered ginger or ginger extracts. Ginger is promoted for alleviating nausea and vomiting during pregnancy. Some evidence supports its use, mainly for alleviating nausea:

• A 2015 Cochrane Review evaluated the use of ginger, among other interventions, for alleviating nausea and vomiting during early pregnancy [199]. The review included 13 studies that examined the effects of ginger as syrup, capsules, or powder within biscuits. The doses of ginger used in the studies varied, but many studies used 1 g/day for several days to a few weeks. The authors concluded that ginger may be helpful, but the overall evidence was not consistent.
• A 2023 meta-analysis included 14 studies that examined the effects of ginger at doses ranging from 500 mg to 2.5 g/day for 4 days to 3 weeks [259]. It found that ginger can be helpful but that it was more effective for alleviating nausea than vomiting. However, the quality of evidence was low for most of the studies.
• A 2024 umbrella review of ginger use during pregnancy included seven meta-analyses (including the two described above) that covered 22 studies [260]. The studies evaluated the use of preparations of powdered ginger, ginger extracts, or brewed ginger. The authors reported that the majority of the meta-analyses found that ginger significantly improved nausea during pregnancy when compared with placebo. However, the quality of the meta-analyses included in the review was described as low to critically low.
• ACOG states that ginger can be considered as a nonpharmaceutical option for alleviating nausea during pregnancy based on limited or inconsistent scientific evidence [205]. However, they add that ginger has not been shown to be effective for reducing vomiting.
• NICE states that there is some evidence that ginger helps treat mild-to-moderate nausea and vomiting during pregnancy [245]. They recommend that health care providers suggest trying ginger for patients who prefer nonpharmaceutical options.
• WHO recommends using ginger to relieve nausea in early pregnancy, but they note that this recommendation is based on low-certainty evidence [86].

In the United States, ginger is generally recognized as safe (GRAS) for its intended use [261]. Ginger use during pregnancy appears to be safe. No adverse effects have been reported in people who use 1 to 2 g daily, although not all studies have assessed adverse effects [247,258].

Peppermint (Mentha piperita)

Peppermint leaf and peppermint leaf essential oil are promoted for alleviating nausea and vomiting during pregnancy [247,248]. Peppermint is often used as inhalation aromatherapy (which is not classified as a dietary supplement), rather than as an oral supplement [247]. However, it is unclear whether peppermint is helpful because the research on its effects is very limited.

In the United States, peppermint is GRAS for its intended use [261], and it is considered safe when consumed in the amounts that are commonly found in foods [262].

Limited information is available on the safety of taking peppermint leaf during pregnancy [258]. According to experts, peppermint leaf essential oil should not be taken during pregnancy except under the supervision of a qualified health care practitioner [258].

Red Raspberry Leaf (Rubus idaeus)

Red raspberry leaf is promoted for strengthening the uterus and facilitating labor, possibly because of its effects on muscle tissue in the uterus [248,263,264]. However, there is very little evidence supporting its use.

A 2021 systematic review of red raspberry leaf use in pregnancy included 13 studies [263]. Six of the studies were in humans, but only one was an RCT. That study used 2.4 g/day raspberry leaf extract from 32 weeks gestation until the start of labor, and it did not find any differences compared with placebo for outcomes such as length of labor or mode of birth. The review authors concluded that the evidence supporting the use of red raspberry leaf during pregnancy is weak.

The safety of using red raspberry leaf during pregnancy has not been well studied, although doses up to 2.4 g/day from 32 weeks gestation until delivery have not been reported to cause adverse effects [258].

Other Botanicals

Whether other botanicals have beneficial effects on pregnancy outcomes has not been established. However, some botanicals may be unsafe to use during pregnancy. The following list provides some examples, but it is not an exhaustive list:

• Some botanicals, such as goldenseal, mugwort, and pennyroyal, may cause uterine contractions or spontaneous abortions [258]. Furthermore, using these botanicals to induce an abortion can cause serious side effects, including liver failure and death.
• Feverfew and licorice root may have adverse effects on the fetus [258].
• Other botanicals, such a fenugreek, sassafras, black cohosh, blue cohosh, and ginkgo, may also be unsafe to use during pregnancy [247,258,265].

Special Considerations During Pregnancy

Twin and Other Multiple Pregnancies

Overview

In the United States, about 3% of births are twins, while less than 0.1% are multiple births that consist of triplets or more [266]. The number of women giving birth to twins and other multiples in the United States has increased over the past several decades, primarily due to the use of assisted reproductive technology but also due to women giving birth at a more advanced age [267,268].

A few studies have examined specific nutrients in women who are pregnant with multiples, but research is very limited. No formal nutrient recommendations exist for women who are pregnant with multiples.

• Observational studies that have compared biomarkers in women with single and twin pregnancies have reported lower concentrations of hemoglobin, serum vitamin D, and umbilical cord DHA in twin pregnancies [268-270].
• Anemia due to folate deficiency is eight times more common in twin pregnancies than in single pregnancies [271].
• One clinical trial found that high-dose folic acid (4–5.1 mg/day) did not reduce the risk of preeclampsia in women who were pregnant with twins compared with placebo [272].
• The few clinical trials that have compared the effects of higher and lower doses of iron have had mixed results:
  • One trial in women who did not have anemia and were carrying twins found that using a daily dose of 54 mg iron was no more effective than a daily dose of 27 mg at preventing iron deficiency anemia. In addition, more side effects were reported in the group that consumed the higher dose [273].
  • A trial in women with iron deficiency who were carrying twins found increases in hemoglobin and ferritin concentrations at 32 weeks in the group that took 68 mg/day iron compared with the group that took 34 mg/day. No other differences in neonatal outcomes or maternal reports of gastrointestinal complaints were found [274].

The authors of a 2015 Cochrane Review were unable to draw conclusions about nutrition for multiple pregnancies due to a lack of evidence [275].

For multiple pregnancies, Alberta Health Services of Canada [254] recommends:

• Following the general nutrition guidelines for single pregnancies.
• Taking only one daily multivitamin supplement (i.e., not doubling the dose). 
• Assessing whether additional calcium, vitamin D, and the omega-3 fatty acids DHA and EPA are needed.

Along with other experts [271], Alberta Health Services of Canada also recommends using higher amounts of folic acid (1,000 mcg/day) in women who are pregnant with multiples [254].

Experts caution against using higher doses of vitamin A in women who are pregnant with twins or other multiples, because high doses can cause congenital birth defects. The vitamin A RDA does not increase for twin or other multiple pregnancies [254,268].

The FNB has not set separate DRIs for women who are pregnant with twins or other multiples.

Vegetarian and Vegan Diets

Overview

Many people follow vegetarian and vegan diets, but few studies have evaluated the impact of these diets on maternal and infant health outcomes. Moreover, vegetarian dietary patterns differ. Vegan diets exclude all foods of animal origin, while vegetarian diets may include some animal-sourced food [276]. For example, lacto-vegetarian diets include dairy, while lacto-ovo vegetarian diets include dairy and eggs.

Overall, limited research suggests that among pregnant women with adequate access to food (i.e., those who avoid animal-based foods by choice), pregnancy outcomes among women who follow vegetarian or vegan diets are similar to those in omnivores, as long as vitamin and mineral needs are met [149,277].

Some evidence links vegetarian and vegan diets during pregnancy with a higher risk of infants born small for gestational age, but this has not been associated with postnatal morbidity. In addition, no associations have been reported between vegetarian or vegan diets and gestational diabetes, gestational anemia, hypertensive disorders of pregnancy, or other maternal outcomes [277-279].

Following a healthy vegetarian dietary pattern during pregnancy can meet most nutrient needs but meeting some micronutrient requirements can be challenging [280]. Studies show that people who follow vegetarian or vegan diets, including those who are pregnant, tend to have lower intakes of vitamin B12, vitamin D, iron, zinc, iodine, calcium, choline, and the omega-3 fatty acids EPA and DHA [97,213,276,277,281,282]. However, it is important to keep in mind that nutrient intakes can differ according to the dietary pattern. For example, lacto-ovo vegetarian diets may contain adequate amounts of calcium while vegan diets may not [149,213].

In general, the recommendations for all pregnant women apply to those who adhere to vegetarian or vegan diets as well. There are currently only a few recommendations that specifically address supplementation in women who are pregnant and adhere to vegetarian or vegan diets.

The Academy of Nutrition and Dietetics states that well-planned vegetarian and vegan diets can be nutritionally adequate during pregnancy [149]. They also recommend the following:

• Special consideration for adequate intakes of iron, zinc, vitamin B12, and EPA and DHA during pregnancy (in addition to protein, calcium, iodine, and vitamin D) for all women who follow vegetarian or vegan diets. They note that vegan sources of EPA and DHA that are derived from microalgae are available as supplements.
• Vitamin B12 supplements or fortified foods, especially for women who follow vegan diets.
• Iron supplementation of 30 mg/day from a prenatal supplement, a separate iron supplement, or a combination of the two.

The 2020–2025 DGA states that a lacto-ovo vegetarian pattern is one of the recommended dietary patterns during pregnancy [17]. The DGA also notes the following:

• Pregnant women who follow a vegetarian or vegan dietary pattern should consult with a health care provider to determine whether supplementation of iron; vitamin B12; and/or other nutrients such as choline, zinc, iodine, or EPA/DHA is necessary. If supplementation is necessary, the health care provider should determine the appropriate levels to meet the patient’s unique needs.
• Obtaining adequate amounts of iron may be a particular concern because plant foods contain only nonheme iron, which is less bioavailable than heme iron.
• Obtaining adequate amounts of vitamin B12 is a concern because this vitamin is present only in foods from animal sources.

The National Health Service in the United Kingdom has similar recommendations [283].

Some professional societies have specific recommendations for pregnant women who follow vegan diets:

• ACOG states that this population may require vitamin and mineral supplementation [14].
• The American Thyroid Association recommends 150 mcg/day iodine supplementation for all pregnant women and states that those who follow vegan diets may need additional supplementation [124,284].

Pregnancy After Bariatric Surgery

Overview

Nearly 40% of women of reproductive age in the United States have obesity, and more than half of all bariatric surgeries are performed in this population [285,286]. Sleeve gastrectomy, Roux-en-Y gastric bypass (RYGB), and adjustable gastric band are the most common types of bariatric surgery.

Although the weight loss that follows bariatric surgery can improve pregnancy outcomes, there are also increased risks of adverse health outcomes, including anemia, congenital abnormalities, preterm birth, low birthweight, and perinatal mortality [285,287-289].

Bariatric surgery also increases the risk of several micronutrient deficiencies. Pregnant women who have undergone bariatric surgery are commonly at higher risk of deficiencies in vitamins A, B12, D, and K; calcium; iron; and folate. However, the effects of surgery vary depending on the type of bariatric procedure [285,289-293]. For example, vitamin A undernutrition may be particularly severe in pregnant women following RYGB [294].

Dietary supplements can reduce micronutrient deficiencies and are commonly recommended for all people following bariatric surgery. However, experts note that standard multivitamins and prenatal supplements may not provide adequate amounts of nutrients, such as vitamin B12, iron, or fat-soluble vitamins, for people who have undergone bariatric surgery [286,290]. In addition, few guidelines are specific to pregnancy following bariatric surgery.

The 2019 Clinical Practice Guidelines from the American Association of Clinical Endocrinologists/American College of Endocrinology, The Obesity Society, American Society for Metabolic and Bariatric Surgery, Obesity Medicine Association, and American Society of Anesthesiologists recommend the following nutrient supplementation for all individuals after bariatric surgery to prevent deficiencies: vitamins A, B12, D, E, and K; thiamin; folic acid; calcium; copper; iron; and zinc [295].

Some recommendations relate specifically to pregnancy after bariatric surgery [295]. Women should avoid getting pregnant for 12 to 18 months post procedure. In addition, health care providers should ensure that these patients receive:

• Counseling and monitoring for appropriate weight gain during pregnancy, nutritional supplementation, and fetal health.
• Screening for nutrient deficiencies every trimester, including vitamin B12, vitamin D, folate, iron, and calcium.
• Additional screening for other fat-soluble vitamins, zinc, and copper if they have had a malabsorptive procedure, such as RYGB.

The British Obesity and Metabolic Surgery Society has similar guidelines [296].

The 2009 ACOG practice guidelines for bariatric surgery and pregnancy recommend nutritional consultation after conception with consideration of a broad evaluation for micronutrient deficiencies [288]. ACOG also notes that pregnant women who have undergone bariatric surgery may require vitamin and mineral supplementation [14].

Sickle Cell Disease

Overview

Sickle cell disease (SCD; also known as sickle cell anemia) is a group of inherited blood disorders that are characterized by misshaped red blood cells [297]. It can cause pain due to blocked blood flow as well as stroke, lung and eye problems, infections, and kidney disease.

In the United States, about 100,000 people have SCD. Although more than 90% of people in the United States with SCD are Black and an estimated 3% to 9% are Hispanic or Latino, race should not be the only factor used to assess genetic risk [298,299].

Pregnant women with SCD have a significantly increased risk of adverse maternal and infant health outcomes, including death [297,299,300]. However, pre-pregnancy counseling and multidisciplinary care can improve outcomes.

In 2024, the Society for Fetal-Maternal Medicine released guidelines for SCD management during pregnancy [299]. It recommends the following for pregnant women who have SCD:

• Maternal baseline assessments of iron and iron stores and hematocrit.
• Maternal baseline assessment of vitamin D and, if needed, supplementation up to 1,000 to 2,000 IU/day (25–50 mcg/day).
• Supplementation with prenatal vitamins that do not contain iron unless iron deficiency is confirmed.
• Supplementation with 4 mg/day folic acid.

ACOG endorses these recommendations [301].

Updated: April 3, 2025