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Nutrition in pregnancy: Dietary requirements and supplements

Nutrition in pregnancy: Dietary requirements and supplements
Literature review current through: May 2024.
This topic last updated: May 08, 2024.

INTRODUCTION — Fetal growth and development during pregnancy requires maternal physiologic adaptation and a change in nutritional needs. Adequate maternal intake of macronutrients and micronutrients promotes normal embryonic and fetal development [1], while undernutrition and overnutrition (eg, an obesogenic environment) may be associated with adverse maternal, pregnancy, and pediatric outcomes, including miscarriage, some congenital anomalies, hypertensive disorders of pregnancy, gestational diabetes, preterm birth, small for gestational age newborn, and suboptimal neurocognitive development [2-9]. Furthermore, a developmental model for the origins of disease (ie, Barker hypothesis) hypothesizes that the fetal environment, which is affected by maternal nutritional and metabolic status, causes epigenetic modifications that impact gene expression and thereby influence subsequent development of disease in offspring, both in childhood and adulthood [10]. Seminal studies of the health status of adult offspring of a cohort of females who were pregnant during the Dutch famine in World War II support this hypothesis [11,12]. More recently, epigenetic changes (altered gene methylation) related to periconception obesity have been associated with an increased risk for metabolic syndrome in offspring [13].

Maternal nutritional status is a modifiable risk factor that can be evaluated, monitored, and, when appropriate, improved. Beginning the modifications before conception is important since addressing diet during pregnancy may not be sufficiently early for some outcomes (eg, folic acid to prevent neural tube defects [NTDs] or occurrence of gestational diabetes related to obesity), but can impact others (eg, gestational weight gain) [9,14]. Ideally, individuals should be at a healthy body mass index (BMI) and have optimal nutritional status when they conceive; however, in reality, approximately 50 percent of females in high-income countries are overweight or obese at the time of conception and many have inadequate micronutrient status, particularly for iron and folate [9,15]. (See "The preconception office visit", section on 'Core interventions'.)

It is important to note the limitations of available evidence. Although some relationships between nutrients and pregnancy outcomes are clear (such as the timing and dose of folic acid needed to prevent NTDs), many questions remain unanswered due to the many challenges of performing high-quality research in pregnancy [16]. These challenges include the often unknown critical windows when nutrition may impact development, the many physiologic changes that occur over the course of normal pregnancy, the large individual differences in maternal adaptation to pregnancy, difficulties with accurately measuring maternal diet, ethical and practical issues of experimenting with pregnant people, challenges with determining effects of specific nutrients in the context of the entire diet, and the lack of an animal model that can be directly extrapolated to humans. Thus, many recommendations for intake are based on observational studies with substantial limitations and expert consensus. Nevertheless, the preponderance of evidence supports a relationship between maternal diet and health of both mother and offspring.

This topic will discuss basic nutritional requirements in pregnancy, primarily for pregnant people living in middle- and high-income countries. Assessment of maternal diet and counseling about dietary issues in these areas are reviewed separately. (See "Nutrition in pregnancy: Assessment and counseling".)

The evaluation and management of undernutrition in pregnancy in resource-limited areas are also reviewed separately. (See "Undernutrition in pregnancy: Evaluation, management, and outcome in resource-limited areas".)

GENERAL DIETARY PRINCIPLES FOR OPTIMAL PREGNANCY OUTCOME — The key components of healthy eating during pregnancy include [17,18]:

Following a healthy dietary pattern, including consumption of [18]:

Vegetables of all types: dark green, red, and orange vegetables; beans, peas, and lentils; starchy vegetables; other vegetables

Fruits, especially whole fruits

Grains, at least half of which should be whole grains

Dairy, including fat-free or low-fat milk, yogurt, and cheese, and/or lactose-free versions and fortified soy beverages and yogurt as alternatives

Protein-rich foods, including lean meats, poultry, and eggs; seafood; beans, peas, and lentils; and nuts, seeds, and soy products

Oils, including plant-based oils and oils in food, such as in seafood and nuts (but not tropical oils, which are high in saturated fatty acids)

A variety of primarily whole, unprocessed foods and beverages should be consumed in appropriate amounts to allow adequate, but not excessive, gestational weight gain. (See "Nutrition in pregnancy: Assessment and counseling", section on 'General principles of a healthy diet during pregnancy'.)

Limiting consumption of added sugars, saturated fat, and sodium – Pregnant people (and others) typically exceed recommended limits for these substances, and this may have negative health consequences. They should focus on increasing intake of high-quality, nutrient-dense foods and attempt to limit intake of processed "empty-calorie" foods and beverages. Avoiding or limiting consumption of highly processed foods is an important means of decreasing consumption of sugar, saturated fat, and sodium.

Appropriate vitamin and mineral supplementation – (See 'Dietary requirements' below.)

Appropriate gestational weight gain – Weight gain is routinely monitored throughout pregnancy. The National Academy of Medicine (formerly the Institute of Medicine [IOM]) has published widely used goals for gestational weight gain (table 1) [19].

Prepregnancy body mass index (BMI) and gestational weight gain have independent, but cumulative, effects on birth weight, maternal weight retention long after giving birth, and possibly gestational duration and risk of childhood obesity; BMI is considered to have the stronger effect. The incidence of pregnancy complications is higher at the upper and lower extremes of BMI and weight gain. (See "Gestational weight gain".)

Avoiding alcohol and other known or potential harmful substances (eg, mercury) – (See "Alcohol intake and pregnancy" and "Fish consumption and marine omega-3 fatty acid supplementation in pregnancy", section on 'Methylmercury in fish'.)

Limiting caffeine intake to less than 200 to 300 mg per day. (See "Nutrition in pregnancy: Assessment and counseling", section on 'Guidelines for safe caffeine intake' and "Caffeine: Effects on reproductive outcomes in females".)

Safe food handling – (See "Nutrition in pregnancy: Assessment and counseling", section on 'Food safety'.)

DIETARY REQUIREMENTS

Background — In 2020, the Dietary Guidelines Advisory Committee of the United States Department of Health and Human Services and United States Department of Agriculture (USDA) published a scientific report of Dietary Guidelines for Americans, which included nutritional guidance for pregnant individuals for the first time [18]. The guidelines incorporated evidence from the most recent research with guidelines from prior sources, including the 1990 Institute of Medicine (IOM, now the National Academy of Medicine) report on nutrition in pregnancy [6], the 2009 IOM report on weight gain in pregnancy [20], the 2006 IOM publication Dietary Reference Intakes: The Essential Guide to Nutrient Requirements [21], and some updates of the dietary reference intakes [22].

The following discussion focuses on the general obstetric population. Other populations, such as those with medical disorders affecting nutrition or residing in severely resource-limited areas, may require additional nutritional considerations.

Recommended dietary allowances (RDAs) are levels of nutrients recommended by an expert IOM panel based on extensive evaluation of available scientific evidence and mathematically adjusted to meet the needs of 97 percent of the population.

Energy intake — Energy intake (also called caloric intake) is a key nutritional factor in determining birth weight. The best way to assess adequacy of energy intake is by monitoring gestational weight gain.

Dietary reference intakes (DRIs) for energy requirements were updated in 2023 based on studies using doubly labeled water methods [23]. The daily estimated energy requirement during the first trimester is the same as for nonpregnant individuals. In the second and third trimesters, the daily estimated energy requirement is calculated based on age, height, prepregnancy weight, weeks of gestation, activity level, and a factor for extra calories needed for energy deposition. The energy deposition/mobilization factor differs by prepregnancy body mass index (BMI). It is + 300 kcal/d for underweight BMI, + 200 kcal/d for normal BMI, + 150 kcal/d for overweight BMI, and –50 kcal/d for obese BMI. Apps to facilitate this calculation are under development.

Macronutrients

Protein — The fetal/placental unit utilizes approximately 1000 g of protein, with most of this requirement in the last six months.

Recommended intake – The RDA for protein during the second and third trimesters of pregnancy is 71 g (1.1 g/kg/day) (table 2), which is higher than the recommendation for nonpregnant people (46 g/day or 0.8 g/kg/day) [18,24]. The increase in protein consumption should be proportional to total calories, as the percent of calories from protein remains at 10 to 35 percent of total kcal for both pregnant and nonpregnant individuals. Some experts have recommended keeping protein consumption below 25 percent of kcal [25].

Reported total protein intake among pregnant individuals in resource-abundant countries is between 14.7 and 16.1 percent of kcal, thus falling within these recommendations.

Sources – Healthy protein sources include lean meats, poultry and eggs, seafood, beans, peas, lentils, nuts, seeds, and soy products. Highly processed meats are not recommended. In the United States, pregnant individuals typically consume excess meats, poultry, and eggs, while consumption of seafood, beans, peas and lentils are below recommendations [18].

We discourage use of special protein powders and high-protein supplements. In pregnant people, especially those who likely have adequate protein intake, high-protein supplements have no measurable benefits and may have harmful effects, such as lower birth weight and higher risk of small for gestational age (SGA) births, although data are not definitive [6,26]. For example:

In analyses of randomized trials of undernourished pregnant people, protein supplementation alone (in contrast to balanced energy and protein supplementation) did not improve clinically important pregnancy outcomes [27-29].

In an observational study of >91,000 pregnant people in Japan, maternal protein intake had an inverse U-curve: Birth weight was highest and risk of SGA was lowest when protein consumption was approximately 12 percent of kcals [30].

In a study of >120,000 pregnant people in Denmark and Norway, high-protein intake did not appear to affect mean birth weight or incidence of low birth weight; however, it was associated with a modest increased risk of preterm birth [31]. (See "Undernutrition in pregnancy: Evaluation, management, and outcome in resource-limited areas", section on 'Balanced energy and protein supplementation'.)

Carbohydrate and fiber

Recommended intake – Carbohydrate requirements increase to 175 g/day in pregnancy, up from 130 g/day in nonpregnant females [18,24]. The Dietary Guidelines for Americans recommend 45 to 65 percent of kcals from carbohydrate for both pregnant and nonpregnant individuals (table 2) [18] since the increase in the carbohydrate requirement is proportional to the increase in pregnancy caloric requirements.

Fiber intake of 28 to 36 g/day is recommended in pregnancy (table 2), which, along with adequate fluid intake, may help prevent or reduce constipation [18]. High fiber consumption prior to conception was associated with a decreased risk of preeclampsia and dyslipidemia in an observational study [32]. High fiber intake may also have favorable effects on blood glucose. (See "Healthy diet in adults", section on 'Fiber'.)

Sources – The focus should be on consuming several servings of whole foods: fruits, vegetables, and whole grains. Highly processed carbohydrates should be minimized to help manage weight gain and avoid high postprandial blood glucose levels, particularly among those with or at high risk of diabetes.

Fat

Recommended intake – The Dietary Guidelines for Americans set daily nutritional goals for pregnant individuals as 20 to 35 percent of total energy intake from fats, <10 percent of total energy from saturated fat, and daily goals for essential fatty acids of 13 g of linoleic acid (18:2) and 1.4 g of linolenic acid (18:3) (table 2) [18]. These goals are consistent with a healthy dietary pattern.

Approximately 75 percent of pregnant people exceed the recommended limit for saturated fat (that from animal products such as meat and dairy, and coconut, palm, and palm kernel oil) [18], which may have negative metabolic consequences.

Sources – Consumption of healthy fats and limiting of saturated fats are recommended. Dietary patterns that provide a healthy profile of fats consistent with the Dietary Guidelines for Americans include the Mediterranean diet (see "Healthy diet in adults", section on 'Mediterranean diet') and the Dietary Approaches to Stop Hypertension (DASH) diet (see "Healthy diet in adults", section on 'DASH diet'). In these diets, plant-derived fats, such as olive oil and nuts, and two to three servings per week of fish comprise the majority of fat intake.

Long-chain polyunsaturated fatty acids — Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are two n-3 (also known as omega-3) long-chain polyunsaturated fatty acids (n-3 LCPUFAs) derived primarily from fish or marine-based sources. DHA is necessary for normal development of the fetal brain and retina, and seafood consumption during pregnancy has also been associated with favorable cognitive development in offspring [33]. N-3 PUFAs have anti-inflammatory effects, which have been associated with a reduction in preterm birth and an increase in mean duration of gestation [34]. N-3 PUFAs have not been effective in preventing gestational diabetes mellitus, and maternal-fetal transport of n-3 PUFAs appears to be blunted in patients with gestational diabetes mellitus [35,36].

Recommended intake – The Dietary Guidelines for Americans recommend that pregnant individuals consume 8 to 12 ounces of seafood per week [18]. The number of weekly servings of fish needed to achieve the DHA intake goal of 200 to 300 mg/day depends on the type of fish, as shown in the table (table 3). Importantly, pregnant people (and those planning to conceive) should choose fish that are low in mercury and other contaminants; a chart to help consumers make appropriate choices is available online. (See "Nutrition in pregnancy: Assessment and counseling", section on 'Guidelines for safe seafood consumption'.)

Sources – Consumption of fish and other marine-based sources is recommended. For pregnant people who are not able or willing to consume fish or adequate amounts of fish, supplementation with n-3 LCPUFAs and consumption of other food sources of n-3 LCPUFA are recommended to achieve an intake of 200 to 300 mg/day of DHA. A number of foods fortified with DHA are available, including yogurt, milk, and eggs. DHA supplements are available either from fish oil or synthesized by algae. Some prenatal vitamins also contain DHA/EPA. (See "Fish consumption and marine omega-3 fatty acid supplementation in pregnancy".)

Lipid-based nutrient supplements are a good source of macro- and micronutrients and have been used to address nutrient requirements in areas where maternal undernutrition is prevalent. (See "Undernutrition in pregnancy: Evaluation, management, and outcome in resource-limited areas", section on 'Lipid-based nutrient supplements'.)

Micronutrients

Overview — Requirements for most micronutrients increase during pregnancy. Requirements for several nutrients (calcium, magnesium, phosphorus, potassium, zinc, and vitamins A, C, and K) vary by maternal age. Recommendations for daily intake of vitamins and minerals during pregnancy for specific age groups are shown in the table (table 2).

Ideally, all or most nutrients can be obtained by eating a diet consisting of nutrient-dense and fortified whole and unprocessed foods and beverages. However, some nutrients (eg, calcium, vitamin D, potassium, fiber, folate/folic acid, iron, iodine, choline) are consistently under-consumed in the United States population.

Multiple-micronutrient supplements

Evidence – In a Cochrane meta-analysis of randomized trials conducted in low- and middle-income countries where the prevalence of micronutrient deficiencies is high, multiple-micronutrient (MMN) supplements in pregnancy appeared to modestly reduce rates of low birth weight (risk ratio [RR] 0.88, 95% CI 0.85-0.91) and SGA (RR 0.92, 95% CI 0.88-0.97), and possibly preterm birth (RR 0.95, 95% CI 0.90-1.01) compared with iron supplementation with/without folic acid [37]. Maternal anemia was reduced when compared with placebo but not when compared with iron supplementation with/without folic acid. There were no demonstrable benefits for several other maternal and pregnancy outcomes: miscarriage, congenital anomalies, maternal mortality, perinatal mortality.

Candidates for MMNs – Most trials of MMNs have been conducted in low-income countries and are not generalizable to high-income countries. Because of a lack of high-quality evidence of the efficacy of MMNs in well-nourished pregnant people, recommendations in high-income countries vary [38]. In the absence of a careful evaluation by a nutritionist, we believe that it is prudent to recommend MMN supplement: Prenatal vitamins are the standard approach.

National health authorities in the United Kingdom do not recommend routine prescription of MMNs for pregnant persons but do recommend specific supplements, such as folic acid and vitamin D [39].

In the United States, MMN supplements are broadly recommended for pregnant people who do not consume an adequate diet [40,41]. In high-income countries, such as the United States, groups at increased risk for micronutrient deficiencies include those carrying a multiple gestation, heavy smokers, adolescents, complete vegetarians (ie, vegans), substance abusers, and individuals who have had bariatric surgery or who have gastrointestinal conditions that cause malabsorption (eg, Crohn disease, bowel resection) [42-45]. These groups can benefit from consultation with dietitians who specialize in maternal nutrition. (See "Nutrition in pregnancy: Assessment and counseling", section on 'Indications for referral to a nutrition professional'.)

Use of MMN supplements among females of reproductive age declined in the US since 2006 but remained unchanged among pregnant people [46]. Well-nourished individuals may not need MMN supplements to satisfy daily requirements; instead, specific supplements (eg, folic acid, iron) would be prescribed to meet individual needs. For example, United States data indicate that while 10 to 48 percent of pregnant people taking MMNs had a total usual intake that was less than the estimated average requirement for some micronutrients, 3 to 48 percent exceeded the adequate intake or the tolerable upper intake level for some micronutrients [47].

World Health Organization (WHO) guidelines recommend use of MMNs in pregnant people receiving antenatal care in any healthcare facility or community-based setting, in the context of rigorous research [48]. Because the evidence for this recommendation was mainly derived from low- and middle-income countries, they state that applicability to high-income countries or to populations not at risk of micronutrient (eg, adequate diet, food fortification programs) is unclear. The evidence was derived from trials using MMNs containing 13 to 15 micronutrients (including iron and folic acid) and the widely available United Nations International Multiple Micronutrient Antenatal Preparation (UNIMMAP), which contains 15 micronutrients (folic acid: 400 mcg, vitamin A: 800 mcg, vitamin D: 200 international units, vitamin E: 10 mg, vitamin B1: 1.4 mg, vitamin B6: 1.9 mg, vitamin B12: 2.6 mcg, niacin: 18 mg, vitamin C: 70 mg, zinc: 15 mg, iron: 30 mg, selenium: 65 mcg, copper: 2 mg, iodine: 150 mcg [49]).

Recommended intake and source – Prenatal vitamins and UNIMMAP account for the majority of MMN supplements taken by pregnant people. The content varies depending on the product used. At a minimum, the daily supplement should contain key vitamins/minerals that are often not met by diet alone, such as iron, folic acid, calcium, vitamin D, and iodine (table 2). In addition to these key vitamins/minerals, the supplement should contain adequate amounts of vitamins A, E, and C; B vitamins; and zinc.

Specific micronutrients are discussed in more detail below.

Iron

Evidence – Iron is necessary for fetal brain and placental development and to expand the maternal red cell mass. Iron deficiency, which is the most prevalent single-nutrient deficiency worldwide [50] and a major cause of anemia,has been estimated to occur in 19 percent of pregnant people in the United States, ranging from 7 percent in the first trimester to 30 percent in the third trimester [51]. More recent studies have reported much higher rates (eg, 30 to 50 percent in the first trimester and 80 percent in the third trimester) [52-54].  

Although systematic reviews have observed that routine iron supplementation in pregnancy consistently results in a reduction in the frequency of iron deficiency anemia at term (eg, RR 0.29, 95% CI 0.17-0.49) [55], clear benefits for mothers or offspring have not been consistently demonstrated for a variety of other outcomes [55,56], even among pregnant people with iron deficiency anemia [57,58]. However, available evidence is generally of low quality. These issues are discussed in detail separately, (See "Anemia in pregnancy", section on 'Treatment of iron deficiency' and "Anemia in pregnancy", section on 'How to screen for iron deficiency'.)

Recommended intake – Dietary reference values for iron in pregnancy vary worldwide [59]. The CDC recommend iron intake of 27 mg/day during pregnancy (up from 18 mg/day in nonpregnant/non-lactating people) to prevent iron deficiency anemia (table 2) [60]. The WHO recommends daily oral iron supplementation with 30 to 60 mg of elemental iron [61]. This amount is readily met by most prenatal vitamin formulations and is adequate supplementation for non-anemic individuals. European and United Kingdom authorities have concluded that additional dietary iron is not needed during pregnancy, provided that iron stores at conception are adequate [62-64]. Of note, in the United States, mean dietary iron intake among pregnant individuals is 17 mg/day from foods alone, and 38 mg/day from foods plus supplements [47]. Importantly, 36 percent of pregnant people consume less than the requirement.

For pregnant people with iron deficiency anemia (first- or third-trimester hemoglobin [Hb] <11 g/dL or second-trimester Hb <10.5 g/dL and low serum ferritin [<40 ng/mL]), an additional iron supplement (30 to 120 mg/day) is required until the anemia is corrected [61,65]. One option is 65 mg of elemental iron (325 mg ferrous sulfate) every other day [66]. Iron absorption decreases with increasing dose, thus larger supplementation amounts are best split into several doses during the day. Intermittent iron supplementation (one to three times per week) appears to be as effective as daily supplementation for preventing anemia at term and is better tolerated and thus may result in better compliance [63,67]. The tolerable upper limit of 45 mg/day set by the National Academy of Medicine (formerly the Institute of Medicine [IOM]) based on gastrointestinal side effects is much lower than international recommendations [68] and has been challenged [69]. Of note, iron absorption increases substantially with advancing gestational age [70,71]. Evidence suggests, however, that this increase is blunted in overweight pregnant individuals [72].

For patients with iron deficiency who do not tolerate oral iron, iron can be administered safely and effectively intravenously [73-75]. (See "Anemia in pregnancy", section on 'Treatment of iron deficiency'.)

Dietary sources – Dietary sources of iron are shown in the table (table 4). There are two dietary forms of iron: heme and non-heme. The most bioavailable form is heme iron, which is found in meat, poultry, and fish. Non-heme iron, which comprises 60 percent of iron in animal foods and all of the iron in plant foods, fortified grains, and supplements, is less bioavailable. Absorption of non-heme iron is enhanced by consumption of vitamin-C-rich foods or muscle tissue (meats, poultry, and seafood) [76], and inhibited by consumption of dairy products and coffee/tea/cocoa. (See "Overview of dietary trace elements", section on 'Iron'.)

Calcium and vitamin D

Calcium

Evidence – Low calcium and vitamin D levels have been associated with adverse health outcomes in mother and child, but it is unclear whether low levels are the causal factor or a marker of poor maternal health. These issues are discussed in detail separately. (See "Vitamin D and extraskeletal health", section on 'Pregnancy outcomes' and "Vitamin D deficiency in adults: Definition, clinical manifestations, and treatment", section on 'Pregnancy' and "Clinical manifestations, diagnosis, and treatment of osteomalacia in adults", section on 'Pregnancy'.)

Fetal skeletal development requires approximately 30 g of calcium across pregnancy, primarily in the last trimester. This total is a relatively small percentage of total maternal body calcium and is easily mobilized from maternal stores, if necessary. Intestinal absorption and renal retention of calcium increase progressively throughout gestation [77].

For pregnant people with low baseline dietary calcium intake (particularly in non-United States populations), high-dose calcium supplementation may reduce the risk of developing a hypertensive disorder of pregnancy [78]. Calcium supplementation does not appear to reduce this risk in healthy, nulliparous pregnant people in whom baseline dietary calcium intake is adequate. Although there may be a benefit for preeclampsia prevention in high-risk populations, further study is required since available information is based upon small numbers of patients and heterogeneity in study populations. These data are reviewed separately. (See "Preeclampsia: Prevention", section on 'Calcium supplementation when baseline dietary calcium intake is low'.)

Calcium supplementation does not appear to reduce the risk of spontaneous preterm birth or low birth weight [79].

Recommended intake – In the United States, the recommended daily allowance for calcium is 1000 to 1300 mg in pregnant and lactating individuals, depending on age (table 2) [80].

Of note, average calcium consumption among pregnant people in the United States is 1090 mg/day from foods and 1300 mg/day from foods plus supplements. An estimated 21 percent of pregnant people consume less than 800 mg/day from foods alone [47].

Sources – Calcium content of selected foods can be found online from the USDA National Nutrient Database.

Vitamin D

Evidence – In addition to its role in calcium and bone homeostasis, vitamin D potentially regulates many other cellular functions. Poor vitamin D status in the perinatal period may have short- or long-term consequences on bone, the immune system, and general health, but the precise threshold for optimal vitamin D status during pregnancy and the effects of high-dose supplementation (4000 to 5000 international units daily) on pregnancy outcomes are not well defined [81-85]. These data are reviewed in detail separately. (See "Vitamin D and extraskeletal health", section on 'Pregnancy outcomes'.)

Recommended intake – The Dietary Guidelines for Americans recommend daily intake of 600 international units during pregnancy [18]. Vitamin D deficiency is estimated to affect between 40 and 98 percent of pregnant individuals worldwide [86].

Most prenatal vitamins contain 400 international units of vitamin D, but some preparations contain as little as 200 or as much as 1000 to 1200 international units. The safe upper limit of vitamin D has not been well studied but was conservatively set at 4000 international units in a 2011 guideline [87]. (See "Vitamin D deficiency in adults: Definition, clinical manifestations, and treatment", section on 'Pregnancy'.)

Sources – Supplements often specify the type of vitamin D they contain. Most prescription prenatal vitamins contain cholecalciferol (D3), but some contain ergocalciferol (D2), and some contain a mixture. Many commercial nonprescription products labeled "vitamin D" (multivitamin supplements, fortified milk, and bread) contain D2 rather than D3. D3 is more readily converted to active forms of vitamin D and is more effective at increasing serum 25-hydroxyvitamin D.

Dermal synthesis after exposure to sunlight is the major natural source of the vitamin. Very few foods naturally contain vitamin D (fatty fish livers are the exception). (See "Overview of vitamin D", section on 'Sources'.)

Folate/folic acid

Evidence – The body of evidence supports the efficacy of folic acid supplementation and dietary fortification to decrease the occurrence and recurrence of neural tube defects (NTDs) by at least 70 percent. These data are reviewed in detail separately. (See "Preconception and prenatal folic acid supplementation", section on 'Folic acid supplementation for preventing NTDs'.)

Folic acid supplementation, usually as part of a multivitamin, has also been associated with a variety of other benefits, including a reduction in risk of hypertensive disorders during pregnancy and occurrence of congenital anomalies other than NTDs. (See "Preconception and prenatal folic acid supplementation", section on 'Effect of folic acid supplementation on other pregnancy outcomes'.)

Recommended intake – The Dietary Guidelines for Americans recommends 0.6 mg/day of folate for pregnant people (table 2) [18]. In addition to consuming a diet rich in folate, the United States Preventive Services Task Force (USPSTF) recommends a daily supplement containing 0.4 to 0.8 mg of folic acid one month before and for the first two to three months after conception to reduce the risk of open NTDs [88,89]. An RDA of 0.6 mg is recommended thereafter to meet the growth needs of the fetus and placenta [40]. Continuing folic acid supplementation after the first trimester prevents the decline in serum folate and rise in homocysteine concentrations that occur when supplementation is discontinued [90]. (See "Preconception and prenatal folic acid supplementation", section on 'Administration'.)

For pregnant people at high risk (eg, history of NTD, use of some antiseizure medications), folic acid recommendations are higher (4 mg/day) and are reviewed separately. (See "Preconception and prenatal folic acid supplementation", section on 'Which pregnancies are at increased NTD risk?'.)

Sources – Dietary sources of folic acid (fortified foods) and folate are shown in the table (table 5). While intake of folate from foods on average meets the recommended daily intake, food folate intake is inadequate in at least 36 percent of pregnant individuals [47], which supports routine supplementation of all females of reproductive age. (See "Preconception and prenatal folic acid supplementation", section on 'Sources'.)

Other micronutrients

Choline

Evidence – Choline is a component of acetylcholine, sphingomyelin, and phosphatidylcholine, thus it is important in the development of the fetal central nervous system and cognition [91]. In a systematic review of human studies, low maternal choline intake was associated with a greater than twofold risk of NTDs [92]. Higher maternal choline intake was associated with better child neurocognitive function. This relationship has been observed in both human and animal studies [91].

Recommended intake – In the United States, pregnant people should consume 450 mg/day of choline from food and supplemental sources (table 2) [93]. US National Health and Nutrition Examination Survey (NHANES) data indicate that usual choline intake among pregnant individuals was 319 mg/day, and only 8.5 percent consumed at or above the recommended amount [94].

Sources – Most prenatal supplements contain between 0 and 50 mg of choline, which is substantially less than the recommended daily amount. Thus, the daily requirement is best met by consumption of good choline sources, such as eggs, meats, poultry, seafood, and dairy. Plant sources, such as navy beans, Brussels sprouts, broccoli, and spinach contain lower amounts of choline; therefore, vegetarians and vegans should seek out supplemental sources of choline.

Zinc

Evidence – Zinc has a role in many biological functions, including normal fetal growth and neuronal development. However, in a 2021 systematic review of 25 randomized trials of zinc versus no zinc/placebo supplementation in pregnancy (>18,000 pregnant people and their offspring), zinc supplementation did not significantly improve any maternal, fetal, or newborn outcome (eg, preterm birth, stillbirth, neonatal death, birthweight, low birthweight, SGA), but the evidence was generally low quality [95].

Recommended intake – In the United States, the recommended daily allowance for zinc is 11 to 12 mg during pregnancy (table 2) [96]. Data from the National Health and Nutrition Examination Survey (2011 to 2014) indicate that mean zinc intake among pregnant individuals is 10.3 mg/day from food alone and 18.4 mg/day from food plus supplements [97]. However, an estimated 11 percent of pregnant people consume less than recommended [47].

Management of pregnant people who are at risk for severe zinc deficiency (eg, active inflammatory bowel disease, acrodermatitis enteropathica, pica) is discussed separately. (See "Zinc deficiency and supplementation in children" and "Pica in pregnancy".)

Sources – Food sources of zinc include meat, poultry, and certain types of seafood (oysters, crab, lobster). Whole grains, cereals, and legumes are also good sources of zinc, but bioavailability is lower due to phytates that bind to and decrease its absorption [98]. In observational studies, zinc intake was lower among pregnant vegetarians than nonvegetarians; however, no differences in zinc status or functional outcomes associated with pregnancy were identified [99].

Iodine

Evidence – Iodine is an essential mineral necessary for production of thyroid hormones. Deficiency has potentially harmful effects, such as maternal and fetal/neonatal hypothyroidism. A 2017 systematic review that examined routine iodine supplementation found insufficient data to reach any clinically useful conclusions on its benefits and harms of preconception, during pregnancy, or postpartum [100]. A 2020 systematic review came to a similar conclusion regarding iodine supplementation for pregnant people residing in areas of mild to moderate iodine deficiency [101], presumably because they are able to physiologically adapt to mildly low iodine intakes and draw from intrathyroidal iodine stores to maintain fetal euthyroidism and enable normal neurodevelopment [102].

Recommended intake – The National Academy of Medicine recommends daily iodine intake of 220 mcg during pregnancy (table 2) and 290 mcg during lactation [103]; the WHO and American Thyroid Association recommend daily iodine intake of 250 mcg for both pregnant and lactating people [104,105]. Furthermore, the American Thyroid Association recommends that individuals who are planning pregnancy, are pregnant, or are lactating supplement their diet with a daily oral multivitamin supplement that contains 150 mcg of iodine in the form of potassium iodide [105].

Excessive intake can be harmful [106]. (See 'Supplements and dietary intake that can be harmful' below.)

Sources – Many prenatal vitamins contain no iodine since requirements are often met with dietary sources, such as iodized salt. In the United States, data suggest that 23 to 56 percent of pregnant people have intake below recommended levels based on urinary iodine concentrations [107,108]. Similar findings have been reported in the United Kingdom and in Sweden [109]. Declining intakes of iodine may be related to increased intake of non-iodized salt from processed foods and in the home (such as sea salt, which contains less iodine than iodized salt). Although pregnant individuals should not be encouraged to start using table salt if they do not already do so, pregnant people should be encouraged to use iodized salt (contains 95 mcg iodine per one-quarter teaspoon) rather than non-iodized, and/or consume cooked seafood that is naturally rich in iodine to attain adequate intake.

Vitamin B12

EvidenceVitamin B12 functions closely with folate and homocysteine and is involved in DNA synthesis and cellular metabolism. Few randomized trials have examined the effects of B12 supplementation in pregnancy on maternal or neonatal outcomes. One systematic review of longitudinal cohort studies reported that lower maternal vitamin B12 plasma levels were associated with higher risk of preterm birth, particularly with vitamin B12 deficiency [110]. No association was found with birth weight. However, a randomized trial of vitamin B12 supplementation (50 mcg daily) during pregnancy conducted in Nepal in which 71 percent of 800 participants were vitamin B12 deficient or marginally deficient (<221 pmol/L [300 pg/mL]) found no benefit from supplementation [111]. Gestational age at birth, birth weight, preterm birth rate, and infant growth and neurodevelopment were similar for both groups despite improved B12 status in mothers and infants.

Recommended intake – In the United States, the recommended daily allowance for vitamin B12 is 2.6 mcg in pregnancy and 2.8 mcg during lactation (table 2) [112]. The majority of pregnant people in the United States meet vitamin B12 requirements, with mean intake from foods of 5.6 mcg/day (more than two times RDA) [47]. For individuals with vitamin B12 deficiency, supplemental vitamin B12 is indicated for maternal health. It is administered parenterally if malabsorption is the cause and orally to those with dietary deficiency and normal absorption. (See "Clinical manifestations and diagnosis of vitamin B12 and folate deficiency" and "Causes and pathophysiology of vitamin B12 and folate deficiencies" and "Treatment of vitamin B12 and folate deficiencies".)

Sources Only animal source foods, such as fish, meat, poultry, eggs, and dairy products, contain vitamin B12; thus, individuals who consume a vegetarian or vegan diet are at higher risk of B12 deficiency and should take a supplement [113].

Vitamin A

EvidenceVitamin A is important in cell division, fetal organ and skeletal growth, maintenance of the immune system, fetal visual development, and maintenance of maternal vision [114]. However, supplementation in nondeficient subjects has not been shown to improve pregnancy outcomes and may increase risk of toxicity.

A pregnant person with moderate deficiency is at higher risk for night blindness, particularly in the third trimester when fetal growth is accelerated, because the fetus will obtain sufficient vitamin A at the expense of maternal stores [115-117]. In some resource-limited countries, vitamin A deficiency is a concern; in addition to maternal night blindness, deficiency puts pregnant people at risk of xerophthalmia, anemia, and susceptibility to infection [118]. By contrast, in resource-abundant countries, excessive intake of vitamin A is the primary concern.

Recommended intakeVitamin A utilization increases slightly during pregnancy; thus, recommended daily intake is increased to 750 to 770 mcg retinol equivalents (2500 to 2560 international units) in pregnancy (versus 700 mcg retinol equivalents [approximately 2330 international units] per day in nonpregnant females) (table 2) [119]. Supplements containing high doses of preformed vitamin A should be avoided (see 'Preformed vitamin A in supplements' below). In the United States, mean daily intake of vitamin A among pregnant individuals is 696 mcg retinol equivalents from foods alone and 1283 mcg retinol equivalents from foods plus supplements [47]. An estimated 15 percent of pregnant people consume less than recommended.

Vitamin A deficiency can be considered a severe public health problem in areas where >5 percent of the population had night blindness in their most recent pregnancy or >20 percent of pregnant people have a serum retinol level <0.7 micromol/L, which has been observed in Southeast Asia and sub-Saharan Africa. In this setting, a daily supplement containing less than 3000 mcg retinol equivalents (10,000 international units) or a weekly supplement containing less than 8500 mcg retinol equivalents (25,000 international units) appears to have some maternal and fetal/neonatal health benefits (eg, reduction in maternal anemia and night blindness) with no evidence of teratogenicity [120,121], but does not reduce maternal or perinatal mortality [122], which was suggested by some early studies.

SourcesVitamin A is found in moderate amounts (300 to 770 mcg retinol equivalents) in many prenatal vitamins, often in the form of beta-carotene (provitamin A).

Vitamin A is present in a variety of foods, and requirements can be met by consuming foods such as milk, fish, eggs, carrots, leafy greens, broccoli, cantaloupe, and squash. Some groups recommend avoiding liver because of its high vitamin A content. (see 'Vitamin A in liver' below).

SUPPLEMENTS AND DIETARY INTAKE THAT CAN BE HARMFUL — The use of self-prescribed over-the-counter supplements is commonplace and has led to numerous case reports of vitamin or mineral toxicities due to overuse. Excessive maternal consumption of some foods can also be potentially toxic to the fetus.

Preformed vitamin A in supplements — Consumption of vitamin supplements containing high doses of preformed vitamin A (greater than 10,000 international units per day [1 international unit = 0.3 retinol equivalents]) appears to be teratogenic [121,123]. In the absence of severe deficiency, pregnant people should avoid consuming multivitamin or prenatal supplements that contain more than 5000 international units (1500 mcg retinol equivalents) of preformed vitamin A. Most supplements contain provitamin A carotenoids such as beta-carotene rather than preformed vitamin A (retinol, retinyl esters); high beta-carotene intakes have not been associated with an increased risk for congenital anomalies [124].

Vitamin A in liver — Some foods are fortified with preformed vitamin A and others are rich in preformed vitamin A (eg, liver). For this reason, some groups (eg, Finnish Food Safety Authority Evira, National Health Service) recommend avoiding liver consumption during pregnancy [125-130]. Limiting the intake of liver and liver products during the first trimester is likely prudent, particularly in high-income countries where vitamin A deficiency is rare.

For pregnant people who commonly consume liver, we advise checking local food composition databases as vitamin A content of livers from different animals vary. For example, in the United States Department of Agriculture (USDA) FoodData Central [131], vitamin A content of liver and liver products varies from 3980 international units in one cooked chicken liver to 78,600 international units in 3 ounces of raw New Zealand lamb liver [132].

Iodine in nutritional supplements and seaweed — Excessive intake of iodine can cause fetal goiter [133-135], but the safe upper limit of iodine intake in pregnancy is unclear. Congenital hypothyroidism has been reported in offspring of pregnant people ingesting 2.3 to 12.5 mg iodine daily (greater than 10 times the recommended dietary allowances [RDA] of 220 mcg, and greater than two times the upper limit of 1100 mcg) (table 2) [133,135]. The cases from the United States were related to excess iodine ingestion from nutritional supplements, and those from Japan were related to diets containing large quantities of kombu, other seaweeds, and instant kombu soups. Nevertheless, excessive iodine intake in the United States is uncommon (<1 percent) [108].

Processed trans fatty acids — Processed trans fatty acids (TFAs) should be minimized or preferably avoided. They may have adverse effects on fetal growth and development by interfering with essential fatty acid metabolism, by direct effects on membrane structures or metabolism, or by replacing maternal intake of the cis essential fatty acids [136]. (See "Dietary fat", section on 'Trans fatty acids'.)

TFAs were previously ubiquitous in processed foods in the United States food supply, but use waned by 2003 when research showing adverse effects on lipids and harmful cardiovascular effects prompted consumers to avoid these foods and the US Food and Drug Administration (FDA) required trans fats declared on the Nutrition Facts label by 2006. In 2015, TFAs were no longer considered "Generally Recognized As Safe" (GRAS) by the FDA and banned as of 2018 [137]. The World Health Organization (WHO) called for the global elimination of trans fat from the food supply in 2018, with an elimination target of 2023 [138]. TFAs are still present in some food items with long shelf-lives, and they are still used in some countries [139].

SUPPLEMENTS WITH NO OR UNCERTAIN PREGNANCY BENEFITS

Vitamin E — In a systematic review of randomized trials, vitamin E supplementation during pregnancy in combination with vitamin C or other supplements or drugs did not improve rates of stillbirth, preterm birth, preeclampsia, or low birth weight [140]. Prior evidence [141] suggested that vitamin E increased self-reported abdominal pain and prelabor rupture of membranes at term; however, preterm prelabor rupture of membranes was not increased [140].

Vitamin C — In a systematic review of randomized trials, vitamin C supplementation during pregnancy either alone or in combination with other supplements had no beneficial or harmful effects [142]. No effects were observed on prevention of stillbirth, preterm birth, preeclampsia, or low birth weight. Vitamin C supplementation alone resulted in a decreased risk of preterm prelabor rupture of membranes; however, the quality of evidence was poor.

Vitamin B6 — Vitamin B6 (pyridoxine) is a coenzyme for more than 100 enzymes in the body, including those involved in metabolism of amino acids, carbohydrates, and lipids and synthesis of neurotransmitters. The majority of pregnant individuals consume an adequate amount of B6 through foods and safely exceed the requirement through a combination of foods plus supplements [47]. A 2015 Cochrane review that included four small trials that examined B6 supplementation during pregnancy found no evidence of clinical benefits [143]. Vitamin B6 has been shown to improve mild to moderate nausea during pregnancy. (See "Nausea and vomiting of pregnancy: Treatment and outcome", section on 'Pyridoxine (vitamin B6) monotherapy'.)

Probiotics — Consumption of probiotic supplements is increasingly popular but caution is warranted regarding use of probiotics during pregnancy, given inconclusive evidence of benefit and risk [144].

Although initial reviews suggested that probiotic use (combinations of certain Lactobacillus and Bifidobacterium strains) during pregnancy may have benefits, such as a reduced risk of inflammatory events and preeclampsia and improved maternal glucose metabolism [145,146], without an increased risk of adverse fetal outcomes [144], subsequent meta-analyses do not support a reduction in risk of developing gestational diabetes mellitus (RR 0.80, 95% CI 0.54-1.20) [147], preeclampsia (RR 1.14, 95% CI 0.84-1.53) [147,148], or preterm birth (RR 1.14, 95% CI 0.84-1.53) [148].

Another meta-analysis of 24 randomized trials examined the effects of maternal probiotic supplementation on the breast milk microbiome and infant gut microbiome and found beneficial effects, including decreased occurrence of infantile colic in breast fed infants (risk ratio 0.30, 95% CI 0.16-0.57) [149]. Obstetric outcomes were not evaluated.

Myo-inositol – Myo-inositol is a nonessential, naturally occurring nutrient in plant-based foods. It is a component of phosphatidylinositol, which is important in membranes and signaling functions. Some evidence suggests that prenatal supplementation with myo-inositol may reduce incidence of gestational diabetes mellitus, hypertensive disorders of pregnancy, and preterm birth [150]. Notably, these trials have been conducted in limited geographic and racial-ethnic groups. Further study is needed that includes individuals of different ethnicities, examines the frequency and timing of supplementation, and compares myo-inositol with other interventions. (See "Gestational diabetes mellitus: Screening, diagnosis, and prevention", section on 'Investigational risk reduction measures of uncertain benefit'.)

FLUID REQUIREMENTS

Water and other fluids — During pregnancy, adequate fluid intake from consumption of beverages (water and other liquids) is estimated to be approximately 2.3 L/day (76 fluid ounces or approximately 10 cups) [151]. Additional water is consumed in foods other than beverages to meet the total adequate intake of 3 L/day. Numerous factors (eg, ambient temperature, humidity, physical activity, exercise, illness) also influence total water needs.

Fluoride — Fluoride supplementation during pregnancy is unnecessary, even though pregnant people who live in areas where water is not fluoridated or who consume only unfluoridated bottled water may not achieve adequate intake of fluoride. (See "Nutrition in pregnancy: Assessment and counseling", section on 'Consumption of nonfluoridated bottled or tap water'.)

SPECIAL POPULATIONS

Multiple gestation – Nutritional requirements and weight gain recommendations are higher in multiple gestations. Guidelines are provided separately. (See "Twin pregnancy: Routine prenatal care", section on 'Nutrition and supplements' and "Twin pregnancy: Routine prenatal care", section on 'Gestational weight gain' and "Triplet pregnancy", section on 'Weight gain'.)

Pregnant patients with diabetes – Medical nutritional therapy for patients with pregestational or gestational diabetes are reviewed separately. (See "Pregestational (preexisting) diabetes mellitus: Antenatal glycemic control", section on 'Medical nutrition therapy' and "Gestational diabetes mellitus: Glucose management and maternal prognosis", section on 'Medical nutritional therapy'.)

Postpartum and breastfeeding – An adequate, balanced diet is believed to be important for replenishment of maternal stores that are expended during the pregnancy, for promoting loss of excess weight, and for nourishing the breastfed infant. Maternal nutrition in the postpartum period, including during lactation, are discussed separately. (See "Maternal nutrition during lactation" and "Overview of the postpartum period: Disorders and complications", section on 'Postpartum weight retention'.)

Pregnant people with undernutrition living in resource-limited areas – Pregnant people with potentially severe undernutrition living in resource-limited areas require careful assessment and a different approach to treatment, which is reviewed separately. (See "Undernutrition in pregnancy: Evaluation, management, and outcome in resource-limited areas".)

Pregnant people with self-imposed dietary restraints and other dietary issues – (See "Nutrition in pregnancy: Assessment and counseling", section on 'Issues regarding self-imposed dietary restraints' and "Nutrition in pregnancy: Assessment and counseling", section on 'Other dietary issues'.)

RESOURCES — The Food and Information Center of the United States Department of Agriculture provides several online resources for pregnant people, including information on folic acid, food safety, foods to avoid, and nutrition.

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Nutrition and supplements in pregnancy".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)

Basics topics (see "Patient education: Nutrition before and during pregnancy (The Basics)" and "Patient education: Health and nutrition during breastfeeding (The Basics)" and "Patient education: Vegetarian diet (The Basics)")

Beyond the Basics topic (see "Patient education: Health and nutrition during breastfeeding (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

Clinical significance – Nutrition is a key modifiable factor that may affect birth outcomes and has long-term effects on the health of both the offspring and the birthing individual. (See 'Introduction' above.)

Key components of healthy eating – The key components of recommended healthy eating, based on consensus guidelines, during pregnancy include (see 'General dietary principles for optimal pregnancy outcome' above):

Appropriate gestational weight gain

Consumption of a variety of primarily whole, unprocessed foods in appropriate amounts to allow adequate, but not excessive, gestational weight gain

Appropriate vitamin and mineral supplementation

Avoidance of alcohol and other known or potentially harmful substances

Safe food handling

Recommended intake – Daily nutritional goals for macronutrients, micronutrients, and vitamins during pregnancy are shown in the table (table 2). (See 'Dietary requirements' above.)

In the first trimester, pregnant people typically do not need to increase their caloric intake. In the second and third trimesters, energy requirements differ by prepregnancy body mass index (BMI) classification, physical activity level, and trimester. (See 'Energy intake' above.)

Adequate fluid intake from consumption of beverages (water and other liquids) is estimated to be approximately 2.3 L/day (76 fluid ounces or approximately 10 cups). (See 'Water and other fluids' above.)

Key nutrients that are important during pregnancy are commonly consumed in inadequate amounts. Ensuring adequate consumption of the following nutrients should be addressed by adjusting dietary intake and/or supplementation (see 'Dietary requirements' above):

Calcium

Vitamin D

Fiber

Folate/folic acid

Iron

Iodine

Choline

Consultation with a nutrition professional, such as a registered dietitian, is advised for patients with obesity, eating disorders, malabsorption, or when concern exists of inadequate diet. (See 'Special populations' above.)

Supplements/dietary intake that can be harmful – Consumption of vitamin supplements containing high doses of preformed vitamin A (greater than 10,000 international units per day [1 international unit = 0.3 retinol equivalents]) appears to be teratogenic. Excessive intake of liver and liver products can also result in excessive intake of vitamin A. (See 'Preformed vitamin A in supplements' above and 'Vitamin A in liver' above.)

Excess iodine ingestion can cause fetal goiter. Iodine is present in nutritional supplements and kombu and other seaweeds. (See 'Iodine in nutritional supplements and seaweed' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Edmund F Funai, MD, Jonathan Gillen-Goldstein, MD, Henry Roque, MD, MS, and Jean M Ruvel, RD, CDE, CDN who contributed to an earlier version of this topic review.

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Topic 453 Version 137.0

References

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