Vitamins in pregnancy

Which nutrient requirements increase in pregnancy?

The NIH states that nutrients such as calcium, choline, folate, iodine, iron, magnesium, omega-3, vitamin A, B6, B12, vitamin D, and zinc play a critical role in pregnancy and may be taken in low amounts. ^[1] The values below are the US Food and Nutrition Board (FNB) values reported by the NIH (ages 19–50, pregnancy); RDA is the recommended dietary allowance, AI is adequate intake, and UL is the tolerable upper intake level. Values may differ between organizations. ^[1]

DFE is “dietary folate equivalent”: according to the NIH, 1 µg DFE equals 1 µg of food folate, 0.6 µg of folic acid from fortified foods or from a supplement taken with food, or 0.5 µg of folic acid from a supplement taken on an empty stomach. ^[1] For iodine, the NIH also reports that WHO, UNICEF, and ICCIDD recommend an intake of 250 µg per day in pregnancy; this is not an RDA but the recommendation of another organization. ^[1] In Türkiye, different sections of the TEMD (Society of Endocrinology and Metabolism of Türkiye) guideline cite different amounts for iodine support in pregnancy; these statements are given side by side in the iodine guide. The upper limit for B6 varies markedly by organization; details are on the B6 page.

Some of the typical additional needs in pregnancy are covered in separate guides.

What do the guidelines say?

The recommendations of organizations differ from one another; the table below gives each organization’s own statement and date side by side. The numbers are statements reported from the guidelines, not personal recommendations.

The conclusion from the table is that there is no single international view on vitamin D: the WHO 2016 statement is “not recommended,” the Endocrine Society 2024 statement is “suggests,” the NICE statement is 10 µg by season and risk, and the Ministry of Health guideline is 1,200 IU from week 12. The organizations differ in scope, date, and target population (WHO is a global antenatal care guideline, NICE is aimed at the UK, and the Ministry of Health guideline at prenatal care in Türkiye); the physician following the pregnant woman determines which applies to the individual. The Ministry of Health guideline describes starting vitamin D support regardless of serum 25(OH)D level, referral for serum calcium, 25(OH)D, and spot urine calcium if there are signs of hypercalcemia, and informing the pregnant woman that sunlight is the most important source of vitamin D. ^[3]

There is a similar distinction for iron: the NIH reports that iron supplementation in pregnancy reduces the risk of iron deficiency and anemia and is recommended by many experts, but that routine iron supplementation in pregnant women with adequate iron levels may have adverse effects. According to the NIH, in NHANES data from 2001–2014 in the US, 27.9% of pregnant women aged 20–40 exceeded the UL (45 mg) in total iron intake from food and supplements. ^[1] This proportion is US data. The Ministry of Health guideline, for its part, describes starting iron support from week 16 in pregnant women without anemia and with a treatment dose in pregnant women in whom anemia is detected. ^[3]

What is avoided in pregnancy?

Preformed vitamin A (retinol) and liver. The NIH reports that excess intake of preformed vitamin A (not beta-carotene and other provitamin A carotenoids) can cause birth defects (teratogenic); the UL for preformed vitamin A in pregnancy is the same as for non-pregnant women (2,800 µg for ages 14–18, 3,000 µg for ages 19–50). ^[1] NICE (NG247, 2025) states that cod liver oil and supplements containing vitamin A (retinol) should be avoided in pregnancy, and that this may include ordinary (non-pregnancy) multivitamins. ^[4] The NHS states that liver and liver products (for example, liver pâté) should not be eaten in pregnancy. ^[6] Vitamin A itself is necessary in pregnancy (RDA 770 µg RAE); the problem is high amounts of the preformed type.

Unnecessarily high amounts. Using a separate iron or folic acid supplement together with a prenatal product can push total intake above the upper limit. The NIH reports that folic acid in prenatal products in the US is generally 800 or 1,000 µg, well above the 400 µg recommended to prevent neural tube defects; that in Canada almost all prenatal products contain 1,000 µg of folic acid, and the intake of pregnant women who consume these products together with fortified foods exceeds the UL (1,000 µg). According to the same source, in an NHANES analysis in the US from 2001–2014, supplement use raised the proportion of pregnant women whose folic acid intake was above the UL to 33.4%. ^[7] In groups at high risk for neural tube defects, the Ministry of Health guideline states that 4–5 mg/day of folic acid is used; this is a physician’s decision. ^[3]

Herbal blends. The NIH states that research in pregnant women is limited, that the variety of content, combination, and preparation of herbal products makes safety assessment difficult, and that caution is needed when considering any herbal supplement in pregnancy because of possible safety concerns. According to the same source, 33% of over-the-counter prenatal supplements and 6% of prescription prenatal supplements contain a herbal ingredient; in herbal products containing caffeine, the amount may not be stated on the label. ^[1] A “natural” or “pregnancy-friendly” label therefore does not show the safety of the content.

Nausea and vitamin B6

The NIH reports that ACOG states that vitamin B6 supplementation, alone or together with doxylamine, is safe and effective in relieving nausea and vomiting of pregnancy; dose and form are not specified in the source. ^[1] Evaluation and choice of treatment for nausea and vomiting is done by the physician. Because upper limits for B6 differ widely by organization, the amount on the product label is considered together with the physician’s recommendation.

Is a prenatal vitamin the same as an ordinary multivitamin?

No. The NIH reports that prenatal product formulations vary widely, for example, some lack iodine, and choline is often present in small amounts. In a 2021 evaluation of 188 US prenatal products, 89% of products contained iron (median 27 mg/serving) and 76% contained iodine (median 150 µg/serving); gummy forms often lacked iron or calcium. ^[1] The NIH reports that the American dietary guidelines (DGA) say some pregnant women may need a separate iodine and choline supplement, because many prenatal products do not contain them or contain little. ^[7] NICE also states that ordinary multivitamins may not be suitable in pregnancy because they can contain retinol (above). The “pregnancy” label of a product and its ingredient list are therefore read together; the physician decides which product is suitable for which pregnant woman. One more note, since thyroid tests are frequently requested in pregnancy: products containing high amounts of biotin can lead to false results in some tests measuring thyroid hormone; sources are given in the biotin guide.

What changes for vegan or vegetarian pregnant women?

The NIH reports that a well-planned vegetarian and vegan diet can be nutritionally adequate in pregnancy; however, the risk of B12 inadequacy is higher in those who do not consume animal foods, B12-fortified food or a B12 supplement can markedly reduce the risk of deficiency, and most prenatal products contain B12. ^[1] NICE states that pregnant women on a restricted diet (for example, vegan) may need to add foods containing B12 to their diet or take a B12 supplement. ^[4] The DGA recommends that women on a vegetarian or vegan diet discuss with a health professional whether supplements are needed for iron, B12, and other nutrients (choline, iodine, EPA, and DHA). ^[7]

What is known about choline?

The NIH/FNB AI for choline in pregnancy is 450 mg. The NIH reports that there is no specific recommendation from professional organizations, public agencies, or public health organizations for choline supplementation in pregnancy; that the DGA recommends that pregnant women eat a variety of choline-containing foods, and that vegans or vegetarians discuss with a physician whether a supplement is needed. ^[1]

What is known and what is not?

Known: Requirements for folate, iron, iodine, and vitamin D increase in pregnancy. High amounts of preformed vitamin A are associated with birth defects. The contents of prenatal products differ from one another. ^[1]

Not known: How the difference of opinion among organizations on in whom and in what context vitamin D supplementation provides benefit will be resolved; current national measurements of nutrient intake in pregnant women in Türkiye and of the content of prenatal products; a guideline-level supplement recommendation for choline.

This guide does not recommend personal products or doses. If there is a pregnancy plan, chronic disease, or medication use, the type, amount, and timing of a supplement are determined by the physician following the pregnant woman.