Vitamins & Supplements · Supplement formula
Prenatal and Postnatal Vitamins
Multi-nutrient products for pregnancy and after birth · also called Prenatal vitamins, pregnancy vitamins, postpartum vitamins, vitaminas prenatales
Prenatal vitamins are mixes of vitamins and minerals sold for use before, during and after pregnancy. The clearest evidence is for folic acid, which lowers neural tube defects such as spina bifida. For the whole product, results on birth weight are mixed and mostly come from poorer countries. Iron can poison young children, and labels do not always match what is inside.
General information, not medical advice. Last substantive update · Not medically reviewed. A named clinician has not signed off on this page. How this page is made
About Prenatal and Postnatal Vitamins
Prenatal and postnatal vitamins are mixes of vitamins and minerals, not one standard formula. Folic acid has the best proof. Evidence for the rest of the mix is mixed, and nothing tests a postnatal vitamin or a gummy. Iron, vitamin A, stacking and label accuracy are the main cautions.
What prenatal and postnatal vitamins are
MedlinePlus describes prenatal vitamins as products used before, during and after pregnancy. They come as a tablet, capsule, gummy or softgel. The sources read do not describe one standard formula, so two products called 'prenatal' can differ.
'Postnatal' and 'postpartum' are not defined by the official pages read. They are marketed to mothers after birth and while breastfeeding, but no trial of such a product was found. No brand is named on this page.
What is usually inside
Official pages name folic acid, vitamin D, iron and, in pregnancy, calcium as the key nutrients. A US lab study of 47 products also looked at choline and iodine and found many labels listed neither. Other products add vitamin B12, vitamin A or beta-carotene, or a separate DHA softgel.
Each ingredient has its own page: folate, iron, iodine, vitamin D, vitamin B12, vitamin A, choline, calcium and fish oil (DHA); see the related list. A regular multivitamin is a different product.
How to read the label
The FDA explains that Daily Value (DV) is a reference amount, and % Daily Value shows how much of it one serving gives. The Supplement Facts label must list certain nutrients when they are present. Check the serving size and whether a tablet or gummy is one serving.
Look for iron, vitamin A (retinol) and any extra folic acid. The meaning of 'proprietary blend' was not researched here. Ask a pharmacist.
Food versus pills
The NHS says it is hard to get the folic acid amount it advises from food alone, while a varied diet helps with most other vitamins and minerals. Folate is in leafy greens, peas, chickpeas and fortified cereals; iron in red meat, beans and fortified cereals; iodine in dairy, eggs and sea fish. Amounts per portion were not read, so none are stated.
Trials on this page tested supplements, not foods.
What the research shows
Folic acid before and early in pregnancy lowered neural tube defects in a Cochrane review of 5 trials. Multi-nutrient products lowered low birth weight in 19 trials compared with iron and folic acid, but 19 of 20 were in low- and middle-income countries and the UK placebo trial did not show it.
For omega-3, choline, iodine and vitamin D the evidence is either on the single nutrient or too thin. For postnatal vitamins and gummies, no study was found.
At a glance
Traditional uses history, not proof
- Sold to fill nutrient gaps before, during and after pregnancy
- UK and US health pages advise certain nutrients in pregnancy, not one fixed formula
Studied for research
- Neural tube defects with folic acid, moderate certainty
- Birth weight and early birth, mixed evidence
- Anaemia and iron levels, moderate certainty
- DHA (omega-3) and early birth, moderate certainty for omega-3 alone
- Choline, iodine and vitamin D, insufficient to very low
- 'Postnatal' vitamins and gummies, insufficient evidence
Main compounds
- Folic acid (folate)
- Iron
- Iodine
- Vitamin D
- Vitamin B12
- Vitamin A or beta-carotene
- Choline
- Calcium
- DHA (omega-3), sometimes separate
Common forms
- Tablets and caplets
- Capsules and softgels
- Gummies
- Prescription prenatal products
Research links: 2010 Cochrane review: folic acid and neural tube defects (5 trials) · 2019 Cochrane review: multiple-micronutrient supplements in pregnancy (20 trials) · 2024 Cochrane review: daily oral iron in pregnancy (57 trials) · 2025 lab study: choline, iodine and metals in 47 prenatal products · 2026 review of reviews: multivitamin and mineral use · Research Library · Genes & Biomarkers Library
What it is and its history
- Accepted scientific name
- Prenatal and postnatal vitamins (multi-nutrient products for pregnancy and after birth)
- Common names
- Prenatal vitamins (English); Pregnancy vitamins (English); Postnatal vitamins (English); Postpartum vitamins (English); Prenatal multivitamin (English); Preconception vitamins (English); Vitaminas prenatales (Spanish); Vitaminas para el embarazo (Spanish); Vitaminas posnatales (Spanish)
- Family or group
- Supplement formula: a mix of vitamins and minerals sold for use around pregnancy.
- Harvest and processing
- Not described in the sources read. MedlinePlus says the products come as a tablet, capsule, gummy or softgel and are usually taken once daily. There is no single standard formula in the sources read, so two products called 'prenatal' can differ.
- Look-alikes and adulterants
- Name: Regular multivitamin; Note: A general-purpose mix; it may lack some nutrients stressed in pregnancy or may contain vitamin A (retinol). See /supplements/multivitamins.; Name: Folic acid on its own; Note: One ingredient with its own trial evidence for neural tube defects. See /supplements/folate-vitamin-b9.; Name: Iron on its own; Note: Studied as a medicine; see /supplements/iron.; Name: DHA / fish oil; Note: Sometimes sold as a separate softgel with prenatal products. See /supplements/fish-oil.; Name: Prescription prenatal vitamins; Note: A 2015 Canadian guideline describes prescription multivitamins that contain a higher folic acid amount than over-the-counter ones; a clinician decides.
- Sustainability and conservation
- Not assessed.
What is inside, and how it may work
What it contains and how those compounds act in cells and animals. Laboratory and animal mechanisms are not proven effects in people.
Main compounds
| Compound | Family | Where it is concentrated | Activity studied | Level of evidence |
|---|---|---|---|---|
| Folic acid (folate) | B vitamin | Prenatal vitamin products Varies by product; not standardised. | The ingredient with trial evidence for lowering neural tube defects. NHS: folate helps form red blood cells. 4 21 24 | Human data |
| Iron | mineral | Prenatal vitamin products Varies by product. | Needed to make red blood cells; low iron can cause anaemia. Some prenatal products contain iron and some do not. 5 24 | Human data |
| Iodine | mineral | Prenatal vitamin products Varies; listed on 25 of 47 products in one study. | Linked to thyroid function; trials measured thyroid outcomes. Listed on about half of the 47 products in a US lab study. 7 2 | Human data |
| Vitamin D | vitamin | Prenatal vitamin products Varies by product. | NHS: helps the baby's bones and teeth develop. 13 24 | Human data |
| Vitamin A (retinol or beta-carotene) | vitamin | Prenatal vitamin products Varies; the form matters. | Needed in small amounts, but too much retinol in pregnancy can harm the baby. 25 1 | Human data |
| Vitamin B12 | vitamin | Prenatal vitamin products Varies by product. | Works with folate; the Canadian guideline suggests B12 inside a folic acid multivitamin. 15 21 | Human data |
| Choline | nutrient | Prenatal vitamin products Varies; listed on 12 of 47 products in one study. | Many women eat less than recommended; benefit for the child's brain not shown. Listed on only 12 of 47 products in a US lab study. 6 2 | Human data |
| Calcium | mineral | Prenatal vitamin products Varies by product. | MedlinePlus: calcium builds the baby's bones and teeth; more is needed in pregnancy. 19 | Human data |
| DHA (omega-3) | fatty acid | Prenatal vitamin products Not in every product. | Added to some prenatal products, often as a separate softgel; trials show fewer early births with omega-3. 12 | Human data |
Mechanisms, receptors and pathways
| Target or pathway | Gene or receptor | What was found | Level |
|---|---|---|---|
| Ingredient-level roles (folate, iron, iodine, vitamin D, calcium) | Not applicable | Each nutrient has its own role (for example iron in red blood cells; vitamin D with calcium for bones). Trials of the whole product do not show which ingredient causes an outcome, so no single mechanism is claimed for the product. 24 19 21 | Background |
| Folate and neural tube closure | Not specified in the sources read | Trials show fewer neural tube defects with folic acid; the exact mechanism was not read from a source. 4 | Human data |
Absorption, metabolism and elimination
- Absorption
- Not researched.
- Distribution
- Not found.
- Metabolism
- Not found.
- Elimination
- Not found.
- Bioavailability
- Not compared across products in the sources read.
Isolated compounds versus whole extracts
The NHS says it is difficult to get the folic acid amount it advises from food alone, and that a varied diet helps with most other vitamins and minerals. A 2022 review found women of childbearing age did not get enough folate from food alone, even from fortified food. Food does not replace a supplement for folic acid, and a supplement does not replace a varied diet.
Nutritional composition
NHS lists foods rich in the main nutrients. Folate: broccoli, Brussels sprouts, leafy greens such as kale and spinach, peas, chickpeas, kidney beans and breakfast cereals fortified with folic acid. Iron: red meat, beans, nuts, dried fruit and fortified cereals. Iodine: milk and dairy foods, eggs, sea fish and shellfish. Vitamin A (retinol): cheese, eggs, oily fish, milk; liver is very rich and the NHS says to avoid it in pregnancy. Vitamin B12: meat, fish, milk, cheese, eggs and fortified cereals; vegans may not get enough from food. Amounts per portion from USDA or NIH were not read, so none are stated. Label terms: the FDA says % Daily Value shows how much a nutrient in one serving contributes to a general daily value, and that the Supplement Facts label must list certain nutrients when present. Label terms such as 'proprietary blend' were not researched.
3 moderate certainty1 mixed findings2 very low certainty4 not enough evidence
What was looked at
The 10 benefits and uses checked for Prenatal and Postnatal Vitamins, each with how strong the evidence is. Tap one to open it.
- Neural tube defects (folic acid before and early in pregnancy)Moderate certainty
- Birth outcomes: birth weight, small babies and preterm birthMixed findings
- Maternal anaemia and iron levelsModerate certainty
- Omega-3 (DHA) in pregnancyModerate certainty
- Choline and the baby's brain developmentNot enough evidence
- Iodine and thyroid health in pregnancyNot enough evidence
- Vitamin D in pregnancyVery low certainty
- After birth and while breastfeeding ("postnatal" vitamins)Not enough evidence
- Child health after pregnancy multivitamin useVery low certainty
- Gummies compared with tabletsNot enough evidence
Lab markers tracked in the studies
Baby birth weightMaternal anaemia (haemoglobin) and iron statusPreterm birthBlood vitamin D (25-hydroxyvitamin D)
What is Prenatal and Postnatal Vitamins good for?
The main studied uses and how strong the human evidence is for each. Most trials tested one nutrient or a category of products, not one shelf product, and results are not added together here.
Benefits, one by one
Each card is a research question, not a promise. Tap a goal to filter. Open a card to see the studies, doses and limits.
Neural tube defects (folic acid before and early in pregnancy)
Moderate certaintyA 2010 Cochrane review of 5 trials in 6,105 women found that daily folic acid, taken before and early in pregnancy, cut the chance of a neural tube defect such as spina bifida. Some trials gave folic acid alone and some gave it inside a vitamin and mineral mix. It found no clear effect on cleft lip or palate, heart defects, miscarriage or other birth defects.
3 studiesFolic acid alone or inside a vitamin and mineral mix. Amounts studied…
Studies, doses and limits
What the trials found
The review pooled 5 trials: 1,949 women had an earlier pregnancy affected by a neural tube defect and 4,156 did not. Folic acid, alone or with other vitamins and minerals, gave fewer neural tube defects than no treatment, placebo or vitamins without folic acid (risk ratio 0.28). The effect on repeat defects was clear (0.32). Only one trial looked at first-time defects: none occurred in the folic acid group, but that result alone was not statistically significant. The review found no short-term side effects. A 2015 Canadian guideline reaches a similar view on neural tube defects, graded as expert and cohort-level evidence.
Results
Folic acid prevents neural tube defects. It is not shown to prevent other birth defects. The UK NHS page says folic acid may also help prevent cleft lip and palate and some heart conditions; the Cochrane review found no clear effect on those.
Effect sizes as reported
Overall RR 0.28 (95% CI 0.15 to 0.52); repeat defects RR 0.32 (0.17 to 0.60); first-time defects RR 0.08 (0.00 to 1.33, not significant).
Why this rating
Moderate: results are consistent across 5 trials, but the review is from 2010, has few trials and gives no GRADE rating in its abstract. The ingredient proven is folic acid; folic acid alone and folic acid inside a mix were pooled, so the review cannot say the other ingredients add anything.
Form and dose studied
Folic acid alone or inside a vitamin and mineral mix. Amounts studied are in the studies table.
Who was studied
Women planning pregnancy or in early pregnancy, with or without an earlier affected pregnancy.
Limits
Small number of trials, some old. Does not show that every prenatal vitamin works this way: it depends on the product containing folic acid.
Why researchers looked
Neural tube defects form in the first weeks of pregnancy, often before a woman knows she is pregnant. Folate is needed for early cell growth, so researchers tested folic acid supplements.
Traditional use
Prenatal vitamins are sold as a mix of vitamins and minerals for use before, during and after pregnancy. Swallowing a pill is not the same as eating the foods that contain these nutrients.
Proposed mechanism Ingredient level background
Not tested for the whole product. Each ingredient has its own known job in the body (for example folate in early cell growth, iron in red blood cells), but the trials below do not show which ingredient in a mix caused a result.
A proposed mechanism does not show that the effect happens in people.
No short-term side effects found. See the Safety tab for stacking and vitamin B12 questions.
Birth outcomes: birth weight, small babies and preterm birth
Mixed findingsA 2019 Cochrane review of 20 trials (141,849 women) found multi-nutrient products gave fewer low-birthweight babies than iron and folic acid alone, with no change in deaths. But 19 of 20 trials were in low- and middle-income countries, and the one UK trial against placebo found little or no effect on birth weight or preterm birth. A 2026 review of reviews was also mixed.
2 studiesMulti-nutrient products with iron and folic acid; the formulas differ…
Studies, doses and limits
What the trials found
In 19 trials against iron with or without folic acid, the multi-nutrient products gave fewer low-birthweight babies (risk ratio 0.88, high-quality evidence), probably fewer small-for-gestational-age babies (0.92) and a small drop in preterm birth that just crossed the line of no effect (0.95). There was no difference in perinatal deaths, newborn deaths or third-trimester anaemia. The one UK trial against placebo found little or no effect on preterm birth, small-for-gestational-age or low birthweight. A 2026 rapid review of 19 meta-analyses linked multivitamin use in pregnancy to fewer small-for-gestational-age births, but not to less preterm birth, stillbirth or low birth weight.
Results
Mixed. The two reviews pooled different trials and reached different results on low birth weight. Where many women are short of nutrients, the mix helped birth weight. Where women are well fed, the evidence does not show a clear benefit.
Effect sizes as reported
Low birthweight RR 0.88 (0.85 to 0.91); small-for-gestational-age RR 0.92 (0.88 to 0.97); preterm RR 0.95 (0.90 to 1.01); very preterm RR 0.81 (0.71 to 0.93); perinatal death RR 1.00 (0.90 to 1.11).
Why this rating
Mixed: the biggest review rates low birthweight as high certainty, but it compares with iron and folic acid in mostly low-income countries. The one placebo trial in the UK and the 2026 review of reviews do not show the same benefit for low birth weight.
Form and dose studied
Multi-nutrient products with iron and folic acid; the formulas differed between trials and are not the same as any one product on a shelf.
Who was studied
Pregnant women, mostly in low- and middle-income countries (19 of 20 trials).
Limits
Different products pooled. Possible publication bias for preterm birth and small-for-gestational-age. The 2026 abstract does not say which findings came from trials and which from observational studies.
Why researchers looked
Pregnant women often fall short on several nutrients at once, so trials tested whether a mix of many vitamins and minerals does better than iron and folic acid alone.
Traditional use
Prenatal vitamins are sold as a mix of vitamins and minerals for use before, during and after pregnancy. Swallowing a pill is not the same as eating the foods that contain these nutrients.
Proposed mechanism Ingredient level background
Not tested for the whole product. Each ingredient has its own known job in the body (for example folate in early cell growth, iron in red blood cells), but the trials below do not show which ingredient in a mix caused a result.
A proposed mechanism does not show that the effect happens in people.
The review reports no important harms for deaths. Side effects were not the focus.
Maternal anaemia and iron levels
Moderate certaintyA 2024 Cochrane review of 57 trials (48,971 women) found daily iron in pregnancy may lower anaemia and low iron at the end of pregnancy, and probably lowers iron-deficiency anaemia. Mothers on iron were also probably less likely to have a low-birthweight baby. Not every prenatal vitamin contains iron.
3 studiesIron alone, iron with folic acid, or iron with other nutrients. Amoun…
Studies, doses and limits
What the trials found
Iron compared with placebo or no iron: anaemia 4.0% versus 7.4% (risk ratio 0.30, low certainty), iron deficiency at term 44% versus 66% (0.51, low certainty), iron-deficiency anaemia at term 5.0% versus 18.4% (0.41, moderate certainty) and low birthweight 5.2% versus 6.1% (0.84, moderate certainty). Little or no difference in preterm birth, newborn death or birth defects. Iron plus folic acid probably reduced anaemia at term (0.44, moderate). For side effects the evidence was very uncertain. The multi-nutrient review found no difference in third-trimester anaemia between a mix with iron and iron alone, but one UK placebo trial found less anaemia (RR 0.66) with the mix.
Results
Iron helps prevent anaemia and low iron in pregnancy. This is evidence about iron as a medicine; a prenatal vitamin helps only if it contains iron.
Effect sizes as reported
Anaemia RR 0.30 (0.20 to 0.47); iron-deficiency anaemia at term RR 0.41 (0.26 to 0.63); low birthweight RR 0.84 (0.72 to 0.99).
Why this rating
Moderate for iron-deficiency anaemia at term and low birthweight, low for anaemia and iron deficiency overall, very uncertain for side effects. The trials mostly tested iron, not prenatal vitamins.
Form and dose studied
Iron alone, iron with folic acid, or iron with other nutrients. Amounts studied are in the studies table.
Who was studied
Pregnant women in many countries, with and without anaemia.
Limits
Certainty ranges from moderate to very low. It cannot tell a woman whether her own iron is low; that needs a blood test.
Why researchers looked
Iron needs rise in pregnancy because blood volume grows. Low iron can cause tiredness and anaemia, so iron is a core part of many prenatal products.
Traditional use
Prenatal vitamins are sold as a mix of vitamins and minerals for use before, during and after pregnancy. Swallowing a pill is not the same as eating the foods that contain these nutrients.
Proposed mechanism Ingredient level background
Not tested for the whole product. Each ingredient has its own known job in the body (for example folate in early cell growth, iron in red blood cells), but the trials below do not show which ingredient in a mix caused a result.
A proposed mechanism does not show that the effect happens in people.
Constipation and stomach upset are common iron side effects; large amounts of iron are dangerous for children. See the Safety tab.
Omega-3 (DHA) in pregnancy
Moderate certaintySome prenatal products add a separate DHA softgel. A 2018 Cochrane review of 70 trials (19,927 women) found omega-3 fats in pregnancy led to fewer early births and fewer low-birthweight babies, but more pregnancies that went past 42 weeks. This is omega-3 on its own, not a prenatal vitamin.
1 studiesOmega-3 supplements or foods; amounts varied by trial.
Studies, doses and limits
What the trials found
Babies born before 37 weeks: 13.4% versus 11.9% (risk ratio 0.89, high-quality evidence). Before 34 weeks: 4.6% versus 2.7% (0.58, high-quality). Pregnancies beyond 42 weeks: 1.6% versus 2.6% (1.61, moderate-quality). Low birthweight fell (0.90, high-quality). Child thinking, vision, language and behaviour showed few differences, mostly low or very low quality. Most trials were in upper-middle or high-income countries.
Results
Omega-3 fats lowered early birth. The trials did not test prenatal vitamins; many prenatal vitamins contain no omega-3.
Effect sizes as reported
Preterm <37 weeks RR 0.89 (0.81 to 0.97); <34 weeks RR 0.58 (0.44 to 0.77); >42 weeks RR 1.61 (1.11 to 2.33); low birthweight RR 0.90 (0.82 to 0.99).
Why this rating
High certainty for preterm birth for omega-3 on its own, but it is rated moderate here because no trial tested omega-3 as part of a prenatal vitamin.
Form and dose studied
Omega-3 supplements or foods; amounts varied by trial.
Who was studied
Pregnant women at low, mixed and high risk.
Limits
Different omega-3 types, timing and amounts were pooled. Only some prenatal products contain DHA.
Why researchers looked
Fish-oil fats were tested for their link to pregnancy length and the baby's growth.
Traditional use
Prenatal vitamins are sold as a mix of vitamins and minerals for use before, during and after pregnancy. Swallowing a pill is not the same as eating the foods that contain these nutrients.
Proposed mechanism Ingredient level background
Not tested for the whole product. Each ingredient has its own known job in the body (for example folate in early cell growth, iron in red blood cells), but the trials below do not show which ingredient in a mix caused a result.
A proposed mechanism does not show that the effect happens in people.
Longer pregnancies past 42 weeks were more common; ask a midwife or doctor. Fish oil has its own page.
Choline and the baby's brain development
Not enough evidenceA 2025 systematic review found the evidence insufficient to support or refute the idea that more choline in pregnancy helps a child's brain development. Most results were null. Many prenatal products do not list choline at all.
2 studiesCholine from diet and supplements; amounts varied.
Studies, doses and limits
What the trials found
The review found 4 randomised trials and 5 observational studies (20 papers). Most brain-development tests did not favour higher choline. Some trials had a single better score in one test, but each trial measured many outcomes and most were null. Observational studies were mixed. Major limits in both trial and observational designs prevented confidence.
Results
Not shown. This is a gap, not a finding of no effect.
Effect sizes as reported
Not pooled.
Why this rating
Insufficient: few trials, many outcomes tested and big limits in the studies.
Form and dose studied
Choline from diet and supplements; amounts varied.
Who was studied
Pregnant women and their children.
Limits
Small number of trials; results depend on which test was chosen.
Why researchers looked
Many pregnant women eat less choline than recommended, and animal studies suggested supplements help the offspring's thinking.
Traditional use
Prenatal vitamins are sold as a mix of vitamins and minerals for use before, during and after pregnancy. Swallowing a pill is not the same as eating the foods that contain these nutrients.
Proposed mechanism Ingredient level background
Not tested for the whole product. Each ingredient has its own known job in the body (for example folate in early cell growth, iron in red blood cells), but the trials below do not show which ingredient in a mix caused a result.
A proposed mechanism does not show that the effect happens in people.
No safety problem was the focus of this review.
Iodine and thyroid health in pregnancy
Not enough evidenceA 2017 Cochrane review found too little evidence on routine iodine supplements before, during or after pregnancy. Iodine lowered postpartum hyperthyroidism but also raised digestive upset in one small trial. Almost all of the evidence came from places with mild to moderate iodine deficiency.
2 studiesIodine supplements; amounts varied.
Studies, doses and limits
What the trials found
11 trials with over 2,700 women contributed data. Postpartum hyperthyroidism was lower with iodine (risk ratio 0.32, low-quality, 3 trials, 543 women). Digestive upset in pregnancy was higher (15.33, very low-quality, one trial, 76 women). No clear differences for hypothyroidism, preterm birth, low birthweight or newborn thyroid measures.
Results
Unclear. The authors could not reach firm conclusions.
Effect sizes as reported
Postpartum hyperthyroidism RR 0.32 (0.11 to 0.91); digestive intolerance RR 15.33 (2.07 to 113.70).
Why this rating
Insufficient: few trials, low-quality evidence and wide ranges; results may not apply where deficiency is severe.
Form and dose studied
Iodine supplements; amounts varied.
Who was studied
Women in mild to moderate iodine-deficient settings.
Limits
Few trials; may not apply where women already take prenatal vitamins with iodine.
Why researchers looked
Iodine is needed to make thyroid hormones, and needs rise in pregnancy.
Traditional use
Prenatal vitamins are sold as a mix of vitamins and minerals for use before, during and after pregnancy. Swallowing a pill is not the same as eating the foods that contain these nutrients.
Proposed mechanism Ingredient level background
Not tested for the whole product. Each ingredient has its own known job in the body (for example folate in early cell growth, iron in red blood cells), but the trials below do not show which ingredient in a mix caused a result.
A proposed mechanism does not show that the effect happens in people.
See label accuracy on the Safety tab: iodine on the label often did not match the lab result.
Vitamin D in pregnancy
Very low certaintyA 2024 Cochrane review, after removing 20 earlier trials on trustworthiness grounds, left 10 studies. Evidence on pre-eclampsia, gestational diabetes and preterm birth was very uncertain. One study suggested less severe postpartum bleeding.
2 studiesVitamin D alone or with other nutrients; amounts varied.
Studies, doses and limits
What the trials found
Vitamin D alone versus placebo or no treatment (8 studies, 2,313 women): very uncertain for pre-eclampsia, gestational diabetes and preterm birth. It may reduce severe postpartum bleeding (risk ratio 0.68, one study of 1,134 women, low certainty) and low birthweight (0.69, but the range includes no effect). Vitamin D combined with calcium and other nutrients: very uncertain.
Results
Not clearly shown for pregnancy outcomes. Vitamin D is also an official advice item; see the Safety tab.
Effect sizes as reported
Severe postpartum bleeding RR 0.68 (0.51 to 0.91); low birthweight RR 0.69 (0.44 to 1.08).
Why this rating
Very low: most outcomes were very uncertain and the review kept only 10 studies after checks.
Form and dose studied
Vitamin D alone or with other nutrients; amounts varied.
Who was studied
Pregnant women.
Limits
Small numbers, high or unclear risk of bias in half the studies.
Why researchers looked
Vitamin D helps the baby's bones and teeth form, and many people have low levels, especially in winter.
Traditional use
Prenatal vitamins are sold as a mix of vitamins and minerals for use before, during and after pregnancy. Swallowing a pill is not the same as eating the foods that contain these nutrients.
Proposed mechanism Ingredient level background
Not tested for the whole product. Each ingredient has its own known job in the body (for example folate in early cell growth, iron in red blood cells), but the trials below do not show which ingredient in a mix caused a result.
A proposed mechanism does not show that the effect happens in people.
No hypercalcaemia was reported in the one study that measured it.
After birth and while breastfeeding ("postnatal" vitamins)
Not enough evidenceNo trial of a product sold as a postnatal or postpartum vitamin was found. What exists is about single nutrients: a trial of vitamin D in breastfeeding mothers and a 2024 Cochrane review of treating anaemia after birth. 'Postnatal' is a marketing word that official pages do not define.
4 studiesNot applicable to a finished product.
Studies, doses and limits
What the trials found
In a randomised trial of 174 breastfeeding mothers (137 finished), a higher vitamin D amount added to a multivitamin gave fewer mothers with a low vitamin D level at 3 months (9% versus 25%) and 6 months (14% versus 30%). Babies' vitamin D, bone mass and body composition did not differ. A 2024 Cochrane review of 33 trials (4,558 women) treated postpartum iron-deficiency anaemia: intravenous iron probably reduced tiredness slightly at 8 to 28 days compared with iron tablets (standardised difference -0.25), and iron tablets probably caused more constipation. That review is about treatment of diagnosed anaemia, not about taking a vitamin. The Cochrane iodine review found postpartum hyperthyroidism lower with iodine (low-quality).
Results
Not shown for a postnatal vitamin as a product.
Effect sizes as reported
Vitamin D low level at 3 months 9% versus 25%; fatigue SMD -0.25 (-0.42 to -0.07), intravenous versus oral iron.
Why this rating
Insufficient: no trial of the product type; the single-nutrient trials are small or about treatment.
Who was studied
Breastfeeding mothers and women with anaemia after birth.
Limits
Single-nutrient evidence. The vitamin D trial gave vitamin D on top of a multivitamin.
Why researchers looked
After birth, a mother may be low in iron after blood loss, and breastfeeding adds demands.
Traditional use
Prenatal vitamins are sold as a mix of vitamins and minerals for use before, during and after pregnancy. Swallowing a pill is not the same as eating the foods that contain these nutrients.
Proposed mechanism Ingredient level background
Not tested for the whole product. Each ingredient has its own known job in the body (for example folate in early cell growth, iron in red blood cells), but the trials below do not show which ingredient in a mix caused a result.
A proposed mechanism does not show that the effect happens in people.
Ask a doctor or pharmacist before using any supplement while breastfeeding.
Child health after pregnancy multivitamin use
Very low certaintyA 2026 review of 19 meta-analyses linked multivitamin use in pregnancy to fewer cancers in children, but the abstract does not say which of these links came from trials and which from observational studies. Observational links can reflect other differences between women who do and do not take vitamins.
1 studiesAny multivitamin and mineral product.
Studies, doses and limits
What the trials found
The rapid review included more than 333,943 pregnancies and 904,947 exposed children. It reports links to fewer small-for-gestational-age births and fewer pediatric cancers, but not to preterm birth, stillbirth or low birth weight. It also notes the studies defined 'multivitamin' very differently.
Results
A possible link, not proven cause.
Effect sizes as reported
Not given in the abstract.
Why this rating
Very low: a review of reviews, mostly observational, abstract only, products not defined.
Form and dose studied
Any multivitamin and mineral product.
Who was studied
Mothers and children in pooled studies.
Limits
Mixed designs, loose product definitions, abstract read only.
Why researchers looked
Researchers asked whether vitamins in pregnancy change a child's later health.
Traditional use
Prenatal vitamins are sold as a mix of vitamins and minerals for use before, during and after pregnancy. Swallowing a pill is not the same as eating the foods that contain these nutrients.
Proposed mechanism Ingredient level background
Not tested for the whole product. Each ingredient has its own known job in the body (for example folate in early cell growth, iron in red blood cells), but the trials below do not show which ingredient in a mix caused a result.
A proposed mechanism does not show that the effect happens in people.
No safety signal reported in the abstract.
Gummies compared with tablets
Not enough evidenceNo study comparing prenatal gummies with tablets or capsules was found. MedlinePlus lists tablets, capsules, gummies and softgels as forms, but does not compare them.
2 studiesGummy, tablet, capsule or softgel.
Studies, doses and limits
What the trials found
A PubMed search for prenatal vitamin gummy versus tablet returned no results on 2026-10-26. The abstract of the 2025 lab survey of 47 prenatal products does not mention results by format.
Results
Not studied.
Why this rating
Insufficient: no study found.
Form and dose studied
Gummy, tablet, capsule or softgel.
Limits
Absence of a search result is not proof that nothing exists.
Why researchers looked
Gummies are easier to swallow for some people, so many ask whether they are as good.
Traditional use
Prenatal vitamins are sold as a mix of vitamins and minerals for use before, during and after pregnancy. Swallowing a pill is not the same as eating the foods that contain these nutrients.
Proposed mechanism Ingredient level background
Not tested for the whole product. Each ingredient has its own known job in the body (for example folate in early cell growth, iron in red blood cells), but the trials below do not show which ingredient in a mix caused a result.
A proposed mechanism does not show that the effect happens in people.
Keep all prenatal vitamins, including gummies, out of children's reach; see iron and children on the Safety tab.
Connections to the rest of health
How Prenatal and Postnatal Vitamins connects to the rest of our health knowledge graph. Every link says what kind of connection it is. A safety link (for example to the liver) is a warning, not a benefit. A study that merely mentions a topic never creates a benefit link.
Explore every connection: goals, body systems, organs, symptoms, genes
A. Wellness goals
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Preventive Wellness | Moderate certainty | Neural tube defects (folic acid before and early in pregnancy): A 2010 Cochrane review of 5 trials in 6,105 women found that daily folic acid, taken before and early in pregnancy, cut the chance of a neural tube defect such as spina bifida. Some trials gave folic acid alone and some gave it inside a vitamin and mineral mix. It found no clear effect on cleft lip or palate, heart defects, miscarriage or other birth defects. | 4 15 24 | |
| Womens Wellness | Moderate certainty | Neural tube defects (folic acid before and early in pregnancy): A 2010 Cochrane review of 5 trials in 6,105 women found that daily folic acid, taken before and early in pregnancy, cut the chance of a neural tube defect such as spina bifida. Some trials gave folic acid alone and some gave it inside a vitamin and mineral mix. It found no clear effect on cleft lip or palate, heart defects, miscarriage or other birth defects. Birth outcomes: birth weight, small babies and preterm birth: A 2019 Cochrane review of 20 trials (141,849 women) found multi-nutrient products gave fewer low-birthweight babies than iron and folic acid alone, with no change in deaths. But 19 of 20 trials were in low- and middle-income countries, and the one UK trial against placebo found little or no effect on birth weight or preterm birth. A 2026 review of reviews was also mixed. | 4 15 24 9 14 5 23 | |
| Energy Vitality | Moderate certainty | Maternal anaemia and iron levels: A 2024 Cochrane review of 57 trials (48,971 women) found daily iron in pregnancy may lower anaemia and low iron at the end of pregnancy, and probably lowers iron-deficiency anaemia. Mothers on iron were also probably less likely to have a low-birthweight baby. Not every prenatal vitamin contains iron. | 5 9 23 | |
| Womens Wellness | Moderate certainty | Omega-3 (DHA) in pregnancy: Some prenatal products add a separate DHA softgel. A 2018 Cochrane review of 70 trials (19,927 women) found omega-3 fats in pregnancy led to fewer early births and fewer low-birthweight babies, but more pregnancies that went past 42 weeks. This is omega-3 on its own, not a prenatal vitamin. | 12 | |
| Brain Health | Moderate certainty | Omega-3 (DHA) in pregnancy: Some prenatal products add a separate DHA softgel. A 2018 Cochrane review of 70 trials (19,927 women) found omega-3 fats in pregnancy led to fewer early births and fewer low-birthweight babies, but more pregnancies that went past 42 weeks. This is omega-3 on its own, not a prenatal vitamin. | 12 | |
| Brain Health | Not enough evidence | Choline and the baby's brain development: A 2025 systematic review found the evidence insufficient to support or refute the idea that more choline in pregnancy helps a child's brain development. Most results were null. Many prenatal products do not list choline at all. | 6 2 | |
| Womens Wellness | Not enough evidence | Choline and the baby's brain development: A 2025 systematic review found the evidence insufficient to support or refute the idea that more choline in pregnancy helps a child's brain development. Most results were null. Many prenatal products do not list choline at all. Iodine and thyroid health in pregnancy: A 2017 Cochrane review found too little evidence on routine iodine supplements before, during or after pregnancy. Iodine lowered postpartum hyperthyroidism but also raised digestive upset in one small trial. Almost all of the evidence came from places with mild to moderate iodine deficiency. | 6 2 7 13 24 3 8 20 27 | |
| Bone Health | Very low certainty | Vitamin D in pregnancy: A 2024 Cochrane review, after removing 20 earlier trials on trustworthiness grounds, left 10 studies. Evidence on pre-eclampsia, gestational diabetes and preterm birth was very uncertain. One study suggested less severe postpartum bleeding. | 13 24 | |
| Womens Wellness | Very low certainty | Child health after pregnancy multivitamin use: A 2026 review of 19 meta-analyses linked multivitamin use in pregnancy to fewer cancers in children, but the abstract does not say which of these links came from trials and which from observational studies. Observational links can reflect other differences between women who do and do not take vitamins. | 14 |
B. Body systems
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Reproductive System | Biological association | Moderate certainty | Studied for: Neural tube defects (folic acid before and early in pregnancy) Studied for: Birth outcomes: birth weight, small babies and preterm birth | 4 15 24 9 14 12 3 8 7 20 |
| Blood Circulatory System | Biological association | Moderate certainty | Studied for: Maternal anaemia and iron levels | 5 9 23 |
| Nervous System | Biological association | Not enough evidence | Studied for: Choline and the baby's brain development | 6 2 |
| Endocrine System | Biological association | Not enough evidence | Studied for: Iodine and thyroid health in pregnancy | 7 2 |
| Bones Joints Muscles | Biological association | Very low certainty | Studied for: Vitamin D in pregnancy | 13 24 |
| Digestive System | Biological association | Not enough evidence | Studied for: Gummies compared with tablets | 27 20 |
E. Health conditions
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Iron poisoning in children | Adverse effect or risk | Review | Very high iron doses can be fatal, particularly for children. Preparation or compound: Iron-containing prenatal vitamins |
11 23 |
| Neural tube defects | Clinically supported | Folic acid before and early in pregnancy lowered neural tube defects in 5 trials. Folic acid, alone or in a vitamin mix, lowered neural tube defects in 5 trials. Preparation or compound: Folic acid |
4 | |
| Vitamin B12 deficiency | Sources differ | NHS says high folic acid can hide B12 deficiency; a Canadian guideline disagrees. Preparation or compound: Folic acid |
21 15 |
I. Biomarkers
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Baby birth weight | Biological association | Mixed findings | Measured in trials: higher birth weight / fewer low-birthweight babies. A lab change is not the same as a health benefit. | 9 5 14 |
| Maternal anaemia (haemoglobin) and iron status | Biological association | Moderate certainty | Measured in trials: less anaemia and iron deficiency. A lab change is not the same as a health benefit. | 5 9 |
| Preterm birth | Biological association | Mixed findings | Measured in trials: fewer early births. A lab change is not the same as a health benefit. | 12 9 14 |
| Blood vitamin D (25-hydroxyvitamin D) | Biological association | Low certainty | Measured in trials: fewer people with low levels. A lab change is not the same as a health benefit. | 3 |
K. Biological pathways
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Folate (vitamin B9) | Preliminary mechanism | Human | Folic acid is the nutrient with trial support for preventing neural tube defects. | 4 |
| Iron | Preliminary mechanism | Human | Used to prevent anaemia in pregnancy; dangerous for children in overdose. | 5 11 |
| Iodine | Preliminary mechanism | Human | Listed on only about half of products tested; thyroid link. | 7 2 |
| Vitamin D | Preliminary mechanism | Human | Official advice item in pregnancy; trial evidence for outcomes is very uncertain. | 13 24 |
L. Active compounds
| Connected to | Kind of connection | Evidence status | Context | Studies |
|---|---|---|---|---|
| Folic acid (folate) | Biological association | Human | The ingredient with trial evidence for lowering neural tube defects. NHS: folate helps form red blood cells. Preparation or compound: Prenatal vitamin products |
4 21 24 |
| Iron | Biological association | Human | Needed to make red blood cells; low iron can cause anaemia. Some prenatal products contain iron and some do not. Preparation or compound: Prenatal vitamin products |
5 24 |
| Iodine | Biological association | Human | Linked to thyroid function; trials measured thyroid outcomes. Listed on about half of the 47 products in a US lab study. Preparation or compound: Prenatal vitamin products |
7 2 |
| Vitamin D | Biological association | Human | NHS: helps the baby's bones and teeth develop. Preparation or compound: Prenatal vitamin products |
13 24 |
| Vitamin A (retinol or beta-carotene) | Biological association | Human | Needed in small amounts, but too much retinol in pregnancy can harm the baby. Preparation or compound: Prenatal vitamin products |
25 1 |
| Vitamin B12 | Biological association | Human | Works with folate; the Canadian guideline suggests B12 inside a folic acid multivitamin. Preparation or compound: Prenatal vitamin products |
15 21 |
| Choline | Biological association | Human | Many women eat less than recommended; benefit for the child's brain not shown. Listed on only 12 of 47 products in a US lab study. Preparation or compound: Prenatal vitamin products |
6 2 |
| Calcium | Biological association | Human | MedlinePlus: calcium builds the baby's bones and teeth; more is needed in pregnancy. Preparation or compound: Prenatal vitamin products |
19 |
| DHA (omega-3) | Biological association | Human | Added to some prenatal products, often as a separate softgel; trials show fewer early births with omega-3. Preparation or compound: Prenatal vitamin products |
12 |
Each connection is stored with the ingredient, the connected record, the kind of connection, the evidence status, the supporting studies, the preparation or compound involved, and a review date (last reviewed October 26, 2026).
Evidence at a glance: what the research found for 10 outcomes
Each outcome below is one thing researchers measured. Certainty is how far the evidence can be trusted, not how well it works. The full studies are on the next tab.
The evidence
The research centre for Prenatal and Postnatal Vitamins. Every record here was checked against PubMed or the publisher's page; we never list a study we have not verified.
Evidence by outcome
Bars show how many studies we found for each outcome, not how well it works. People are added up across trials only (reviews are not added, to avoid double counting).
How we rate evidence
High certainty
Several well-run trials or reviews agree; further research is unlikely to change the picture much.
Moderate certainty
Good trials point the same way, but some doubt remains.
Low certainty
Small, short or inconsistent trials. The finding could change with better research.
Very low certainty
Very little or very weak human data. Treat as a possibility only.
Mixed findings
Trials or reviews disagree with each other.
Not enough evidence
Not enough human research to say either way.
Evidence against
Good research found no benefit, or found harm.
We take the reviewers' own risk-of-bias and GRADE statements where they exist, and otherwise judge from study size, design, consistency, directness and whether a product matches what is sold. Many publications do not make evidence high. Method note: We started from our existing prenatal summary, then re-read PubMed abstracts for every review, trial and lab study cited. Only abstracts were read. NHS, MedlinePlus and FDA pages were read in full on 2026-10-26. NIH Office of Dietary Supplements pages were blocked and are marked unverified.
Study library: every study we checked 27
| Study | Design | People | Product, dose, length | Result |
|---|---|---|---|---|
| Abadie 2023 Vitamin A-Mediated Birth Defects: A Narrative Review. Cureus · PMID 38226115 · DOI |
Narrative review |
Narrative review of vitamin A deficiency and excess in pregnancy | Vitamin A Diet and supplements Pregnancy |
The review says both too little and too much vitamin A in pregnancy can harm the baby. Too much can cause defects of the baby's central nervous system. It notes that widespread, unregulated use of multivitamins and supplements makes intakes above recommended levels more common in developed countries. Not applicable (Not applicable) Methods, limits and fundingOutcomes: Birth defects from vitamin A deficiency or excess Limitations: Narrative review, not a systematic search. No numbers in the abstract. Funding and conflicts: Authors declare no competing interests. Read: abstract |
| Borgelt 2025 Content of selected nutrients and heavy metals in prenatal multivitamins and minerals: an observational study. Am J Clin Nutr · PMID 40252729 · DOI |
Laboratory analysis n/a |
47 47 prenatal multivitamin and mineral products (32 nonprescription, 15 prescription) from online retailers and local pharmacies |
Prenatal multivitamin and mineral products tested in a lab Tablets, capsules and other forms sold in the US · vs Label claims; United States Pharmacopeia (USP) metal limits |
Choline was listed on 12 of 47 products (25.6%); 5 were within 20% of the label, 2 were more than 20% over and 5 were more than 20% under. Iodine was listed on 25 of 47 (53.2%); 4 were within 20% of the label, 20 (80%) were more than 20% under and 1 was more than 20% over. Arsenic was measurable in 7 products (14.9%), lead in 32 (68.1%) and cadmium in 29 (61.7%), but none passed USP limits. 20 of 25 iodine-labelled products more than 20% under label; lead measurable in 32 of 47 (Not applicable) Methods, limits and fundingOutcomes: Choline and iodine content versus label; arsenic, lead and cadmium Limitations: Convenience sample from the US market, not the whole market. Only choline, iodine and three metals were measured. The authors' conclusion that products are "misleading through omission or inaccurate content" and call for regulation is their opinion. Funding and conflicts: The first author reports financial support from the Center for Science in the Public Interest; other authors report none. Read: abstract |
| Czech-Kowalska 2014 Impact of vitamin D supplementation during lactation on vitamin D status and body composition of mother-infant pairs: a MAVID randomized controlled trial. PLoS One · PMID 25232839 · DOI |
Randomised controlled trial |
174 174 healthy breastfeeding mothers after term delivery; 137 (79%) finished |
Vitamin D (cholecalciferol) on top of a multivitamin Oral 1,200 IU a day (800 plus 400 from multivitamins) or 400 IU a day (placebo plus 400 from multivitamins) (studied in the trial) 6 months · vs 400 IU a day group |
Mothers on the higher amount were less likely to have a low vitamin D level (under 20 ng/ml) at 3 months (9% versus 25%) and 6 months (14% versus 30%). Babies' vitamin D levels, bone mass and body composition did not differ between groups. Low vitamin D level at 3 months 9% versus 25%; at 6 months 14% versus 30% (Not given in the abstract) Methods, limits and fundingOutcomes: Mother and baby vitamin D blood levels, bone mass, body composition Limitations: Tested vitamin D amounts on top of a multivitamin, not a "postnatal vitamin" as a product. Healthy women only; all babies were also given vitamin D. Funding and conflicts: Authors declare no competing interests. Registration: NCT01506557 Read: abstract |
| De-Regil 2010 Effects and safety of periconceptional folate supplementation for preventing birth defects. Cochrane Database Syst Rev · PMID 20927767 · DOI |
Systematic review meta analysis |
6105 5 randomised or quasi-randomised trials, 6,105 women (1,949 with a previous pregnancy affected by a neural tube defect, 4,156 with none) |
Folic acid, alone or with other vitamins and minerals, before and in early pregnancy Oral Varied by trial (see the review) Before and early in pregnancy · vs No intervention or placebo, or vitamins and minerals without folic acid |
Daily folic acid, alone or with other vitamins and minerals, prevented neural tube defects. The result was strongest for preventing a repeat NTD in women with an affected earlier pregnancy. Only one trial looked at first-time NTDs; there were no cases in the folic acid group but the result was not statistically significant on its own. No clear effect on cleft palate, cleft lip, heart defects, miscarriage or other birth defects. No short-term side effects were found. NTDs overall RR 0.28; repeat NTD RR 0.32; first-time NTD RR 0.08 (not significant) (NTDs overall 0.15 to 0.52; repeat 0.17 to 0.60; first-time 0.00 to 1.33) Methods, limits and fundingOutcomes: Neural tube defects (NTDs), other birth defects, miscarriage, side effects Limitations: Small number of trials, several old, and the review found no trials on blood folate or anaemia at term. Folic acid alone and folic acid inside a multi-nutrient product were pooled, so the review cannot say whether the extra ingredients add anything for NTDs. Funding and conflicts: Cochrane review; the Department of Health (England) is listed as a funder. No conflict statement in the record read. Read: abstract |
| Finkelstein 2024 Daily oral iron supplementation during pregnancy. Cochrane Database Syst Rev · PMID 39145520 · DOI |
Systematic review meta analysis |
48971 57 trials, 48,971 women; 40 compared iron with placebo or no iron, 8 compared iron plus folic acid with placebo or no iron plus folic acid |
Daily oral iron, alone or with folic acid or other vitamins and minerals Oral Varied by trial Pregnancy · vs Placebo or no iron |
Iron may reduce anaemia (4.0% versus 7.4%) and iron deficiency at term (low-certainty), and probably reduces iron-deficiency anaemia at term (5.0% versus 18.4%, moderate). Mothers on iron were probably less likely to have low-birthweight babies (moderate). Little or no difference in preterm birth, newborn death or birth defects. Evidence on side effects was very uncertain. Anaemia RR 0.30; iron-deficiency anaemia at term RR 0.41; low birthweight RR 0.84; preterm birth RR 0.93; adverse effects RR 1.29 (Anaemia 0.20 to 0.47; iron-deficiency anaemia 0.26 to 0.63; low birthweight 0.72 to 0.99; preterm 0.84 to 1.02; adverse effects 0.83 to 2.02) Methods, limits and fundingOutcomes: Maternal anaemia, iron deficiency, birth outcomes, side effects Limitations: Certainty ranged from moderate to very low. It tests iron as a medicine, not prenatal vitamins as a product. Funding and conflicts: Cochrane review. No conflict statement in the record read. Read: abstract |
| Gould 2025 Choline During Pregnancy and Child Neurodevelopment: A Systematic Review of Randomized Controlled Trials and Observational Studies. Nutrients · PMID 40077755 · DOI |
Systematic review |
4 randomised trials of choline in pregnancy and 5 observational studies, reported in 20 publications | Choline during pregnancy Diet and supplements Varied by study Pregnancy · vs Lower or no extra choline |
Most outcomes did not support a benefit of higher choline in pregnancy. Some trials had one test where children of supplemented mothers scored better, but each trial measured many outcomes and most were null. Observational studies were mixed. The authors judged the evidence insufficient to support or refute a benefit. Not pooled (Not applicable) Methods, limits and fundingOutcomes: Child brain development and behaviour tests Limitations: Few trials, many outcomes tested, major limits in both trials and observational studies. Funding and conflicts: Authors declare no conflict of interest; funders had no role. Read: abstract |
| Harding 2017 Iodine supplementation for women during the preconception, pregnancy and postpartum period. Cochrane Database Syst Rev · PMID 28260263 · DOI |
Systematic review meta analysis |
2700 14 studies included, 11 trials with over 2,700 women contributed data; almost all in places with mild to moderate iodine deficiency |
Iodine supplements before, during or after pregnancy Oral Varied by trial Before, during or after pregnancy · vs No iodine or placebo |
The authors found too little data for firm conclusions. Iodine lowered postpartum hyperthyroidism (low-quality) and raised digestive upset in pregnancy (very low-quality, one trial). No clear differences in hypothyroidism, preterm birth, low birthweight or newborn thyroid measures. Postpartum hyperthyroidism RR 0.32; digestive intolerance RR 15.33 (Postpartum hyperthyroidism 0.11 to 0.91; digestive intolerance 2.07 to 113.70) Methods, limits and fundingOutcomes: Thyroid problems, preterm birth, birthweight, perinatal death, adverse effects Limitations: Few trials, low-quality evidence, wide ranges, and may not apply where deficiency is severe or where women already take prenatal vitamins with iodine. Funding and conflicts: Cochrane review. No conflict statement in the record read. Read: abstract |
| Jensen 2024 Treatment for women with postpartum iron deficiency anaemia. Cochrane Database Syst Rev · PMID 39670550 · DOI |
Systematic review meta analysis |
4558 33 randomised trials, 4,558 women with postpartum iron deficiency anaemia (haemoglobin 12 g/dL or lower, treated within six weeks of birth); most trials at high risk of bias |
Intravenous iron, oral iron, red-cell transfusion, erythropoietin (treatments, not routine vitamins) Oral tablets and injections Varied by trial Within 6 weeks of birth · vs Each other, placebo or no treatment |
Intravenous iron probably reduced tiredness slightly at 8 to 28 days compared with iron tablets, with little or no difference after four weeks. Iron tablets probably caused much more constipation than intravenous iron. Evidence on deaths and severe allergic reactions was very uncertain. Breastfeeding was not reported. Fatigue SMD -0.25 (intravenous versus oral iron, 8 to 28 days) (Fatigue -0.42 to -0.07) Methods, limits and fundingOutcomes: Fatigue, anaemia symptoms, constipation, serious reactions Limitations: This is about treating women who already have anaemia after birth, not about taking a postnatal vitamin to prevent it. Most evidence low or very low certainty. Funding and conflicts: No dedicated funding. One author received payment from a Danish centre for writing time. Read: abstract |
| Keats 2019 Multiple-micronutrient supplementation for women during pregnancy. Cochrane Database Syst Rev · PMID 30873598 · DOI |
Systematic review meta analysis |
141849 20 trials (141,849 women); 19 in low- and middle-income countries compared multiple-micronutrient (MMN) products with iron and folic acid against iron with or without folic acid; 1 UK trial compared MMN with placebo |
Multiple-micronutrient supplements containing iron and folic acid Oral products (formulas varied by trial) Varied by trial Pregnancy · vs Iron with or without folic acid (19 trials); placebo (1 UK trial) |
Against iron and folic acid: fewer low-birthweight babies, probably fewer small-for-gestational-age babies, and a small drop in preterm birth that just crossed the line of no effect. No difference in perinatal or newborn deaths or in third-trimester anaemia. The single UK placebo trial found little or no effect on preterm birth, small-for-gestational-age or low birthweight, but fewer mothers with anaemia in the third trimester. Low birthweight RR 0.88; small-for-gestational-age RR 0.92; preterm birth RR 0.95; very preterm RR 0.81; perinatal death RR 1.00; UK placebo trial: third-trimester anaemia RR 0.66 (Low birthweight 0.85 to 0.91; small-for-gestational-age 0.88 to 0.97; preterm 0.90 to 1.01; very preterm 0.71 to 0.93; perinatal death 0.90 to 1.11; third-trimester anaemia (UK trial) 0.51 to 0.85) Methods, limits and fundingOutcomes: Low birthweight, small-for-gestational-age, preterm birth, stillbirth, newborn deaths, maternal anaemia Limitations: Nearly all trials were in low- and middle-income countries and compared with iron and folic acid, not placebo, so it does not show what a prenatal vitamin adds in a well-fed woman. Funnel-plot asymmetry for preterm birth and small-for-gestational-age points to possible publication bias. Results differed by product type and by mothers' body size. Funding and conflicts: Cochrane review. One author led a trial included in the review but was not involved in its screening or data extraction. Public and charitable funding is not detailed in the abstract. Read: abstract |
| Ledowsky 2022 Women Taking a Folic Acid Supplement in Countries with Mandatory Food Fortification Programs May Be Exceeding the Upper Tolerable Limit of Folic Acid: A Systematic Review. Nutrients · PMID 35807899 · DOI |
Systematic review |
Studies since 1998 of folate and folic acid intake in women of childbearing age and in pregnancy, in countries with mandatory food fortification | Folate from food, fortified food and folic acid supplements Diet and supplements |
Women of childbearing age did not get enough folate from food alone, even from fortified food. But almost all women taking a folic acid supplement exceeded the upper tolerable limit. The authors call for a review of supplement advice and the limit. Almost all supplement users above the limit (Not applicable) Methods, limits and fundingOutcomes: Total folate intake compared with the upper tolerable limit of 1,000 micrograms of folic acid a day Limitations: The harm of going above the limit was not shown here. The authors argue the limit was set to avoid masking vitamin B12 deficiency, not from folic acid metabolism. Funding and conflicts: Authors declare no conflict of interest. Read: abstract |
| McGuigan 1996 Acute iron poisoning. Pediatr Ann · PMID 8775917 · DOI |
Narrative review |
Review of acute iron poisoning, especially in young children | Medicinal iron preparations, with or without vitamins Oral Toxicity thresholds as reported in the review (see results) Single ingestion |
Iron poisoning is serious, especially in young children, and the products involved are mostly adult iron preparations with or without vitamins. Stomach and bowel harm follows swallowing about 20 mg of elemental iron per kg of body weight; whole-body toxicity may follow at least 60 mg per kg. Poison-centre or toxicology advice usually leads to a good outcome. Not applicable (Not applicable) Methods, limits and fundingOutcomes: Toxic doses and treatment Limitations: A 1996 review without new data. A single toxic dose has not been established. Funding and conflicts: No funding or conflict statement in the record read. Read: abstract |
| Middleton 2018 Omega-3 fatty acid addition during pregnancy. Cochrane Database Syst Rev · PMID 30480773 · DOI |
Systematic review meta analysis |
19927 70 randomised trials, 19,927 women at low, mixed or high risk of poor pregnancy outcomes; most trials in upper-middle or high-income countries |
Omega-3 long-chain fatty acids (supplements or foods) Supplements and foods Varied by trial Pregnancy · vs Placebo or no omega-3 |
Fewer babies born before 37 weeks (13.4% versus 11.9%) and before 34 weeks (4.6% versus 2.7%), rated high-quality evidence. More pregnancies lasted beyond 42 weeks (1.6% versus 2.6%), moderate-quality. Fewer low-birthweight babies (high-quality). Little or no difference in child thinking, vision, language or behaviour (mostly low or very low quality). Preterm birth <37 weeks RR 0.89; <34 weeks RR 0.58; prolonged pregnancy >42 weeks RR 1.61; low birthweight RR 0.90 (<37 weeks 0.81 to 0.97; <34 weeks 0.44 to 0.77; >42 weeks 1.11 to 2.33; low birthweight 0.82 to 0.99) Methods, limits and fundingOutcomes: Preterm birth, prolonged pregnancy, birth weight, maternal and child outcomes Limitations: This is omega-3 on its own, not a prenatal vitamin. Many prenatal vitamins do not contain omega-3, and the review does not say how much a prenatal vitamin with DHA would add. Funding and conflicts: Cochrane review. Authors state none known; one author's institution has received grants from public and charitable funders for related work. Medical Research Council listed. Read: abstract |
| Palacios 2024 Vitamin D supplementation for women during pregnancy. Cochrane Database Syst Rev · PMID 39077939 · DOI |
Systematic review meta analysis |
2313 10 included studies after a trustworthiness check removed 20 earlier trials; the main comparison was 8 studies in 2,313 pregnant women |
Vitamin D, alone or with calcium and other vitamins and minerals Oral Varied by study Pregnancy · vs Placebo or no intervention |
Evidence was very uncertain for pre-eclampsia, gestational diabetes and preterm birth. Vitamin D alone may reduce severe postpartum bleeding and low birthweight, but the bleeding result came from one study and the low-birthweight range includes no effect. Combined vitamin D, calcium and other nutrients: very uncertain. Severe postpartum bleeding RR 0.68 (one study); low birthweight RR 0.69 (Severe postpartum bleeding 0.51 to 0.91; low birthweight 0.44 to 1.08) Methods, limits and fundingOutcomes: Pre-eclampsia, gestational diabetes, preterm birth, low birthweight, severe postpartum bleeding, adverse events Limitations: After the trustworthiness check only 10 studies remained, and certainty is low or very low. Funding and conflicts: Cochrane review. No conflict statement in the record read. Read: abstract |
| Wang 2026 Multivitamin and mineral use: A rapid review of meta-analyses on health outcomes. Ageing Res Rev · PMID 41308839 · DOI |
Rapid review of meta analyses |
19 meta-analyses (2000 to 2025), including more than 333,943 pregnancies and 904,947 children exposed before birth to a mother's multivitamin | Multivitamin and mineral (MVM) supplements, any formula Oral Varied Varied · vs Varied |
In pregnancy, multivitamin use was linked to fewer small-for-gestational-age births and fewer cancers in children, but not to less preterm birth, stillbirth or low birth weight. The review noted that studies defined a "multivitamin" in very different ways. Not given in the abstract (Not given in the abstract) Methods, limits and fundingOutcomes: Health outcomes in adults and children; in pregnancy: small-for-gestational-age, preterm birth, stillbirth, low birth weight, childhood cancers Limitations: A review of reviews. The abstract does not say which pregnancy findings came from trials and which from observational studies. Observational links can be due to other differences between women who do and do not take vitamins. Funding and conflicts: The competing-interest statement lists relationships for at least one author (for example board membership of a research consortium); details were not fully read. Read: abstract |
| Wilson 2015 Pre-conception Folic Acid and Multivitamin Supplementation for the Primary and Secondary Prevention of Neural Tube Defects and Other Folic Acid-Sensitive Congenital Anomalies. J Obstet Gynaecol Can · PMID 26334606 · DOI |
Clinical practice guideline |
Canadian guideline (SOGC) on folic acid and multivitamin use before and after conception, based on literature searches to June 2014 | Folic acid with or without a multivitamin Oral Describes three Canadian product types: ordinary multivitamins with 0.4 to 0.6 mg folic acid, prenatal multivitamins with 1.0 mg and prescription multivitamins with 5.0 mg Before conception through breastfeeding |
Guideline says folic acid in a multivitamin is needed to reach red-cell folate levels linked to the best protection, and that folic acid is unlikely to mask vitamin B12 deficiency (it suggests B12 in the multivitamin to address even theoretical concerns). It lists reported links between folic acid and epigenetic changes in the fetus (changes in how genes are switched on) and a higher chance of twins. Recommendations are graded III-A to II-2A (expert and cohort-level evidence). Not applicable (Not applicable) Methods, limits and fundingOutcomes: Neural tube defects and other folic-acid-sensitive birth defects; safety concerns Limitations: A guideline, not a trial. Written for Canada and dated 2015. Its view on B12 masking differs from the UK NHS page. Funding and conflicts: No funding or conflict statement in the record read. Read: abstract |
| Zamil 2021 Risk of Birth Defects From Vitamin A "Acne Supplements" Sold Online. Dermatol Pract Concept · PMID 34123566 · DOI |
Label survey n/a |
49 49 vitamin A-containing "acne supplements" sold online in the US, checked March to May 2020 |
Acne supplements (not prenatal vitamins) Online products |
Of 49 products, 26 (53%) contained vitamin A. Three were likely teratogenic (could harm a developing baby), 4 had more vitamin A than most people need, and 15 had unknown risk. Of 6 products with over 10,000 IU of vitamin A, 2 had no pregnancy warning. The authors say US labelling rules for vitamin A can confuse buyers. 2 of 6 high-vitamin-A products had no pregnancy warning (Not applicable) Methods, limits and fundingOutcomes: Vitamin A content and pregnancy warnings on labels Limitations: This is a different product type (acne supplements), so it shows a labelling risk with vitamin A in supplements generally, not what prenatal vitamins contain. Funding and conflicts: One author serves on an advisory board for a skin-care company and wrote a consumer diet book; others report no conflicts. Read: abstract |
| s-fda-dv FDA: Daily Value on the Nutrition and Supplement Facts Labels (content current as of 5 March 2024) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-fda-supplements FDA: Information for Consumers on Using Dietary Supplements (content current as of 21 October 2022) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-medlineplus-pregnancy MedlinePlus Health Topic: Pregnancy and Nutrition · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-medlineplus-prenatal MedlinePlus Drug Information: Prenatal Vitamins (last revised 15 March 2025) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-nhs-folate NHS: Vitamins and minerals, B vitamins and folic acid (page last reviewed 3 August 2020) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-nhs-iodine NHS: Vitamins and minerals, Iodine (page last reviewed 3 August 2020) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-nhs-iron NHS: Vitamins and minerals, Iron (page last reviewed 3 August 2020) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-nhs-pregnancy NHS: Pregnancy vitamins and supplements (page last reviewed 3 June 2026) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-nhs-vitamin-a NHS: Vitamins and minerals, Vitamin A (page last reviewed 3 August 2020) · Source |
Reference database n/a |
Methods, limits and fundingRead: full-text | ||
| s-ods-folate NIH Office of Dietary Supplements: Folate fact sheet for health professionals · Source |
Reference database n/a |
Methods, limits and fundingRead: not-read | ||
| s-search-gummies PubMed search record: "prenatal vitamin gummy versus tablet" (2026-10-26) · Source |
Search record n/a |
Methods, limits and fundingRead: search-record |
What we do not know yet
- No trial compared a prenatal vitamin with a regular multivitamin.
- Most multi-nutrient trials were in low- and middle-income countries and used iron and folic acid as the comparison.
- No trial of a postnatal or postpartum vitamin was found.
- No study compared gummies with tablets.
- NIH Office of Dietary Supplements pages could not be read, so US upper limits are not stated.
- NHS pages on folic acid, iron, iodine and vitamin A were last reviewed in 2020.
- Label terms such as 'proprietary blend' and food amounts per portion were not researched.
How new research is added
New studies are found by a saved PubMed search and placed in a review queue before the page changes.
Lab markers
What changed in blood or saliva tests during trials. A changed number is not the same as feeling or being healthier, and we give no "normal ranges".
Other 4
Baby birth weight
Higher birth weight / fewer low-birthweight babies in trials
How much a baby weighs at birth. "Low birthweight" means under 2,500 grams. "Small for gestational age" means smaller than expected for the weeks of pregnancy.
Mixed findingsResults and what it means
Why it was measured
A common measure of how well a pregnancy went and a predictor of early health.
Statistical vs. clinical meaning
A population measure. It does not tell any one woman whether a product helped her baby.
Safety implication
None specific.
| Study | Result | People | Product |
|---|---|---|---|
| 9 | Low birthweight RR 0.88 versus iron and folic acid; small-for-gestational-age RR 0.92; UK placebo trial: little or no effect | 20 trials, 141,849 women | Multi-nutrient products |
| 5 | Low birthweight 5.2% versus 6.1% with iron (RR 0.84) | 12 trials, 18,290 infants | Daily oral iron |
| 14 | No link between multivitamin use in pregnancy and low birth weight; link to fewer small-for-gestational-age births | 19 meta-analyses | Multivitamin and mineral |
Maternal anaemia (haemoglobin) and iron status
Less anaemia and iron deficiency in trials
Haemoglobin is the protein in red blood cells that carries oxygen. Anaemia means it is low. Iron deficiency means the body's iron stores are low.
Moderate certaintyResults and what it means
Why it was measured
Iron levels are checked in routine pregnancy blood tests, because low iron causes tiredness and anaemia.
Statistical vs. clinical meaning
A blood test result, but anaemia is also what mothers feel as tiredness.
Safety implication
Iron also causes constipation and stomach upset in some people.
Preterm birth
Fewer early births in trials
A baby born before 37 weeks of pregnancy.
Mixed findingsResults and what it means
Why it was measured
Early birth is a leading cause of newborn health problems.
Statistical vs. clinical meaning
Omega-3 reduced early birth; multi-nutrient products did not clearly.
Safety implication
Longer pregnancies past 42 weeks were more common with omega-3.
| Study | Result | People | Product |
|---|---|---|---|
| 12 | Before 37 weeks: 13.4% versus 11.9% with omega-3 (RR 0.89); before 34 weeks: 4.6% versus 2.7% (RR 0.58) | 70 trials, 19,927 women | Omega-3 fats (not a prenatal vitamin) |
| 9 | RR 0.95 (0.90 to 1.01) for multi-nutrient versus iron and folic acid; just crossed no effect | 18 trials, 91,425 participants | Multi-nutrient products |
| 14 | No link between multivitamin use in pregnancy and preterm birth | 19 meta-analyses | Multivitamin and mineral |
Blood vitamin D (25-hydroxyvitamin D)
Fewer people with low levels in trials
A blood test that shows how much vitamin D the body holds.
Low certaintyResults and what it means
Why it was measured
To see if a supplement raises or maintains vitamin D levels.
Statistical vs. clinical meaning
Raises the blood level; babies' levels, bone and body composition did not differ.
Safety implication
None reported.
| Study | Result | People | Product |
|---|---|---|---|
| 3 | Low level (under 20 ng/ml) in 9% versus 25% at 3 months and 14% versus 30% at 6 months with the higher amount | 137 breastfeeding mothers | Vitamin D plus multivitamin |
Safety
What studies and official sources say about side effects, medicines and who should check first. Each point shows what kind of evidence it comes from.
Main points to know 5
- Iron in prenatal vitamins can poison young children. The NHS says very high doses of iron can be fatal, particularly if taken by children. A 1996 review says the products involved in poisonings are mostly adult iron preparations, with or without vitamins; stomach and bowel harm is reported after about 20 mg of iron per kg of body weight and whole-body poisoning from at least 60 mg per kg. Not every prenatal vitamin contains iron. MedlinePlus says to keep the container tightly closed and out of children's reach, and gives the US poison helpline (1-800-222-1222). Review and official guidance 11 23 20
- Vitamin A (retinol) in pregnancy: check the label. The NHS says not to take supplements containing vitamin A (retinol), or cod liver oil, in pregnancy, because too much can harm the baby's development. MedlinePlus says very high vitamin A can cause birth defects. A 2023 narrative review says too much vitamin A in pregnancy can cause defects of the baby's central nervous system and that unregulated supplement use makes high intakes more common. A 2021 survey of acne supplements found 2 of 6 high-vitamin-A products had no pregnancy warning, so labels can fail to warn. Official guidance, narrative review and label survey 24 25 19 1 16
- Stacking: the same nutrient in several products. A prenatal vitamin plus a separate folic acid, iron, vitamin D, fish-liver-oil or multivitamin product can repeat the same nutrient. A 2022 review found that in countries with folic acid in food, almost all women taking a folic acid supplement were above the 1,000 microgram upper tolerable limit. In pages last reviewed in 2020 the NHS names amounts it calls unlikely to cause harm for supplements (1 mg folic acid, 17 mg iron, 0.5 mg iodine), and its 2026 pregnancy page says not to take more than 100 micrograms of vitamin D a day. These are the NHS statements, not advice to take any amount. Ask a midwife, doctor or pharmacist to add up everything you take. Systematic review and official guidance 10 21 23 22 24
- Labels may not match what is inside. A 2025 lab study of 47 US prenatal products found choline listed on only 12 and iodine on 25. Of the 25 that listed iodine, 20 held more than 20% less than the label said. Lead was measurable in 32 products and cadmium in 29, though none went over United States Pharmacopeia limits. The FDA says it is not authorized to approve supplements for safety and effectiveness before they are sold. Laboratory analysis and regulator statement 2 18
- Folic acid and vitamin B12: sources disagree. The NHS says folic acid doses above 1 mg a day can mask the signs of vitamin B12 deficiency, which can damage the nervous system if not found. A 2015 Canadian guideline says folic acid is unlikely to mask B12 deficiency and suggests B12 inside the multivitamin. State only what both agree on: B12 deficiency matters, and a doctor can test for it. Official guidance and guideline (sources differ) 21 15
Side effects 5
| Effect | How often | Severity and recovery | Evidence |
|---|---|---|---|
| Constipation, nausea, vomiting, diarrhoea MedlinePlus lists these as common side effects of prenatal vitamins. The NHS adds that high amounts of iron cause constipation, feeling sick, being sick and stomach pain. | Not given | Mild; tell a doctor if severe or lasting Not stated | Official drug information 20 |
| Itching, rash or hives (possible allergic reaction) MedlinePlus says to call a doctor immediately. | Not given | Can be serious Not stated | Official drug information 20 |
| Side effects of iron in pregnancy trials The Cochrane review rated this very low certainty. For iron plus folic acid, one trial reported more side effects (low certainty). | 21.6% versus 18.0% (not a clear difference) | Not described in the abstract Not stated | Systematic review 5 |
| Digestive upset with iodine in pregnancy Very low-certainty evidence. | One trial of 76 women | Not described Not stated | Systematic review 7 |
| Longer pregnancies past 42 weeks with omega-3 (DHA) Applies only to products that contain omega-3. | 1.6% versus 2.6% | Not described Not stated | Systematic review 12 |
Liver
No liver injury from prenatal vitamins was found in the sources read. Liver as a food is very rich in vitamin A, and the NHS says to avoid liver and liver products in pregnancy. Whether prenatal vitamins affect people with liver disease was not described in the sources read. 25
How often. No frequency found.
Monitoring. No agency monitoring advice was found.
This is a safety connection. It is not evidence that Prenatal and Postnatal Vitamins supports liver health.
Medicines and supplements 5
| With | Why it matters | Importance | Evidence | What to do |
|---|---|---|---|---|
| Prescription and over-the-counter medicines (general) prescription | No mechanism given. | MedlinePlus says to tell your doctor and pharmacist about all medicines, vitamins and herbal products, because doses of other medicines may need changing or you may need to be watched for side effects. It names no specific medicine. | Official drug information Not enough evidence 20 | Keep a written list of everything you take and show it to your doctor or pharmacist. |
| Other supplements: separate folic acid, iron, vitamin D, vitamin A or fish liver oil supplement | Same nutrient taken twice. | Totals can pass the amounts the NHS calls unlikely to cause harm, or the 1,000 microgram folic acid upper tolerable limit; 2022 review found this common for folic acid supplements. | Systematic review and official guidance Low certainty 10 23 24 | Add up all products with a midwife, doctor or pharmacist. |
| Vitamin B12 deficiency condition | NHS: high folic acid can mask the symptoms of B12 deficiency, which can eventually damage the nervous system if it is not spotted. | NHS and the Canadian guideline disagree on whether folic acid masks B12 deficiency. | Official guidance (sources differ) Mixed findings 21 15 | Ask a doctor about a B12 test if you are unsure. |
| Epilepsy medicine, HIV medicine, diabetes and some blood conditions condition | Not described. | The NHS says people in these groups, or with certain birth-defect history, may be given a higher folic acid dose by a GP. This is a prescribing question, not a reported interaction. | Official guidance Not enough evidence 24 | Ask your GP or midwife. |
| Bleeding problems, anaemia, surgery (including dental) condition | Not described. | MedlinePlus says to tell your doctor if you have these or are having surgery. | Official drug information Not enough evidence 20 | Tell the doctor or dentist. |
Who should check first 5
| Situation | Advice | Evidence |
|---|---|---|
| Products with vitamin A (retinol) during pregnancy | The NHS says not to take supplements containing vitamin A (retinol) in pregnancy and to always check the label. Ask a midwife or pharmacist. | Official guidance 24 19 |
| Children in the home (iron) | Keep prenatal vitamins out of reach. If a child may have swallowed them, call the poison helpline or emergency services. | Official guidance and review 20 23 11 |
| Pregnancy and breastfeeding (the intended groups) | MedlinePlus says to tell your doctor if you are pregnant, planning pregnancy or breastfeeding. Official pages read do not describe a separate product for "postnatal" use. | Official drug information 20 |
| Allergy to a vitamin or any ingredient | MedlinePlus says to tell your doctor and pharmacist about any allergy, and what symptoms you had. | Official drug information 20 |
| Kidney or liver disease | Not described in the sources read. Ask a doctor. | Absence of evidence |
Overdose, product quality and regulators
Summary. Acute poisoning is mainly about iron in children. Other nutrients carry risks mainly from long-term high intake or stacking.
Animal. Not reviewed.
High dose or long term signals. NHS statements: long-term vitamin A above 1.5 mg a day from food and supplements may affect bones; high iodine for long periods can change thyroid function; more than 100 micrograms of vitamin D a day could be harmful; more than 1 mg folic acid a day can hide B12 deficiency.
Overdose response. MedlinePlus: in an overdose call the poison helpline (US 1-800-222-1222); if the person has collapsed, had a seizure, has trouble breathing or cannot be woken, call 911. For other countries use your local poison centre.
Genotoxicity. Not researched.
Quality is not checked by the regulator before sale in the US. One lab study of 47 prenatal products looked at two nutrients and three metals. A different product type, acne supplements, showed that vitamin A labels can fail to warn pregnant women.
Iodine and choline versus label. Iodine was listed on 25 of 47 products; 20 held more than 20% under the label. Choline was listed on 12; 5 were more than 20% under and 2 more than 20% over. 2
Heavy metals. Arsenic measurable in 7 products, lead in 32 and cadmium in 29 of 47; none exceeded USP limits. 2
Vitamin A labels on other supplements. Of 49 online acne supplements, 26 contained vitamin A; 2 of 6 with over 10,000 IU had no pregnancy warning. 16
Regulator premarket approval. FDA is not authorized to approve dietary supplements for safety and effectiveness before they are marketed. 18
| Body | Action | Date |
|---|---|---|
| NHS (UK) (United Kingdom) | Pregnancy page advises folic acid and vitamin D supplements, says to avoid supplements with vitamin A (retinol) and cod liver oil, says not to take more than 100 micrograms of vitamin D a day, and says iron levels are checked at the first midwife visit and around 28 weeks. Amounts are on its page. source | 2026-06-03 |
| NHS (UK), B vitamins and folic acid (United Kingdom) | Says doses of folic acid above 1 mg a day can mask vitamin B12 deficiency, and 1 mg or less a day from supplements is unlikely to cause harm. source | 2020-08-03 |
| NHS (UK), Vitamin A (United Kingdom) | Says long-term intake above an average of 1.5 mg (1,500 micrograms) a day from food and supplements may affect bones; many multivitamins and fish liver oils contain vitamin A; avoid liver in pregnancy. source | 2020-08-03 |
| NHS (UK), Iron (United Kingdom) | Says very high doses of iron can be fatal, particularly if taken by children; 17 mg or less a day of iron supplements is unlikely to cause harm; over 20 mg can cause constipation, sickness and stomach pain. source | 2020-08-03 |
| NHS (UK), Iodine (United Kingdom) | Says high doses of iodine for long periods can change how the thyroid works, and 0.5 mg or less a day from supplements is unlikely to cause harm. source | 2020-08-03 |
| MedlinePlus (US National Library of Medicine) (United States) | Describes prenatal vitamins as used before, during and after pregnancy; forms include tablet, capsule, gummy and softgel; lists side effects; says to tell the doctor about all medicines and supplements; gives the poison helpline for overdose. source | 2025-03-15 |
| MedlinePlus, Pregnancy and Nutrition (United States) | Says more folic acid, iron, calcium and vitamin D are needed in pregnancy; that very high vitamin A can cause birth defects; and to take only supplements a health care provider recommends. source | |
| US Food and Drug Administration (United States) | States it is not authorized to approve dietary supplements for safety and effectiveness before they are marketed; advises talking to a doctor or pharmacist. source | 2022-10-21 |
| Society of Obstetricians and Gynaecologists of Canada (SOGC) (Canada) | 2015 guideline on folic acid and multivitamins before and after conception; says folic acid is unlikely to mask B12 deficiency. source | 2015 |
When to get medical help
- Swelling of the face, lips or tongue, hives, wheezing or trouble breathing after taking a vitamin: get emergency help.
- A child who may have swallowed prenatal vitamins: call the poison helpline at once (US 1-800-222-1222) or your local poison centre, even if the child seems well.
- A person who has collapsed, had a seizure, has trouble breathing or cannot be woken after swallowing vitamins: call 911 or your local emergency number.
- Itching, rash or hives after starting a product: call a doctor immediately (MedlinePlus).
- Concerns about vitamin A in a product you already took while pregnant: speak to a midwife or doctor.
Stop using the product and contact a clinician or emergency service. In the US, Poison Control is 1-800-222-1222.
General information only, not medical advice. Ask a clinician or pharmacist before use, especially with medicines, in pregnancy or with a health condition. See the Natural Remedy Safety guide.
Frequently asked questions
What are prenatal and postnatal vitamins?
They are mixes of vitamins and minerals sold for use before, during and after pregnancy. MedlinePlus lists tablet, capsule, gummy and softgel forms. There is no single standard formula in the sources read.
Do prenatal vitamins prevent birth defects?
Folic acid does lower neural tube defects such as spina bifida: a Cochrane review of 5 trials cut the risk to about a quarter (RR 0.28). It found no clear effect on other birth defects. Not every prenatal vitamin has folic acid, so check the label.
Is a prenatal vitamin better than a regular multivitamin?
No study was found that compares the two as finished products. They can differ in vitamin A, iron and folic acid. MedlinePlus says to read the label and ask your pharmacist.
Do prenatal vitamins improve birth weight?
Do they help with anaemia?
Iron does: a Cochrane review of 57 trials found daily iron probably lowers iron-deficiency anaemia at term. Only products that contain iron can do this, and a blood test shows whether iron is low.
Is vitamin A in prenatal vitamins safe?
Can the iron in prenatal vitamins harm children?
Do the labels match what is inside?
Not always. In a 2025 lab study of 47 US prenatal products, 20 of 25 that listed iodine held more than 20% less than the label said.
Can prenatal vitamins contain heavy metals?
In the same study, lead was measurable in 32 of 47 products and cadmium in 29, but none went over United States Pharmacopeia limits. It was a convenience sample, not the whole market.
Are prenatal gummies as good as tablets?
Do postnatal or postpartum vitamins work?
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Editorial transparency
- Written by
- AlternativeMed editorial team. Research compiled with AI assistance, then checked against the sources listed.
- Medical review
- None. This page has not been reviewed by a physician or pharmacist.
- First published
- 2026-10-26
- Last substantive update
- 2026-10-26
- How we research
- We started from our existing prenatal summary, then re-read PubMed abstracts for every review, trial and lab study cited. Only abstracts were read. NHS, MedlinePlus and FDA pages were read in full on 2026-10-26. NIH Office of Dietary Supplements pages were blocked and are marked unverified.
- How we rate evidence
- See "How we rate evidence" in the Evidence tab.
- Independence
- No product is promoted on this page. No brand names or affiliate links are shown. Funding is flagged where the abstracts show it.
Sources 27
Each source was opened and checked. Where we read only the abstract, it says so. The small numbers in the text point here.
- Abadie RB, Staples AA, Lauck LV et al.. Vitamin A-Mediated Birth Defects: A Narrative Review.. Cureus. 2023. PMID 38226115. DOI 10.7759/cureus.50513. (abstract)
- Borgelt LM, Armstrong M, Brindley S et al.. Content of selected nutrients and heavy metals in prenatal multivitamins and minerals: an observational study.. Am J Clin Nutr. 2025. PMID 40252729. DOI 10.1016/j.ajcnut.2025.04.013. (abstract)
- Czech-Kowalska J, Latka-Grot J, Bulsiewicz D et al.. Impact of vitamin D supplementation during lactation on vitamin D status and body composition of mother-infant pairs: a MAVID randomized controlled trial.. PLoS One. 2014. PMID 25232839. DOI 10.1371/journal.pone.0107708. (abstract)
- De-Regil LM, Fernández-Gaxiola AC, Dowswell T et al.. Effects and safety of periconceptional folate supplementation for preventing birth defects.. Cochrane Database Syst Rev. 2010. PMID 20927767. DOI 10.1002/14651858.CD007950.pub2. (abstract)
- Finkelstein JL, Cuthbert A, Weeks J et al.. Daily oral iron supplementation during pregnancy.. Cochrane Database Syst Rev. 2024. PMID 39145520. DOI 10.1002/14651858.CD004736.pub6. (abstract)
- Gould JF, Hines S, Best KP et al.. Choline During Pregnancy and Child Neurodevelopment: A Systematic Review of Randomized Controlled Trials and Observational Studies.. Nutrients. 2025. PMID 40077755. DOI 10.3390/nu17050886. (abstract)
- Harding KB, Peña-Rosas JP, Webster AC et al.. Iodine supplementation for women during the preconception, pregnancy and postpartum period.. Cochrane Database Syst Rev. 2017. PMID 28260263. DOI 10.1002/14651858.CD011761.pub2. (abstract)
- Jensen MCH, Holm C, Jørgensen KJ et al.. Treatment for women with postpartum iron deficiency anaemia.. Cochrane Database Syst Rev. 2024. PMID 39670550. DOI 10.1002/14651858.CD010861.pub3. (abstract)
- Keats EC, Haider BA, Tam E et al.. Multiple-micronutrient supplementation for women during pregnancy.. Cochrane Database Syst Rev. 2019. PMID 30873598. DOI 10.1002/14651858.CD004905.pub6. (abstract)
- Ledowsky C, Mahimbo A, Scarf V et al.. Women Taking a Folic Acid Supplement in Countries with Mandatory Food Fortification Programs May Be Exceeding the Upper Tolerable Limit of Folic Acid: A Systematic Review.. Nutrients. 2022. PMID 35807899. DOI 10.3390/nu14132715. (abstract)
- McGuigan MA. Acute iron poisoning.. Pediatr Ann. 1996. PMID 8775917. DOI 10.3928/0090-4481-19960101-08. (abstract)
- Middleton P, Gomersall JC, Gould JF et al.. Omega-3 fatty acid addition during pregnancy.. Cochrane Database Syst Rev. 2018. PMID 30480773. DOI 10.1002/14651858.CD003402.pub3. (abstract)
- Palacios C, Kostiuk LL, Cuthbert A et al.. Vitamin D supplementation for women during pregnancy.. Cochrane Database Syst Rev. 2024. PMID 39077939. DOI 10.1002/14651858.CD008873.pub5. (abstract)
- Wang W, Wazny VK, Mahadzir MDA et al.. Multivitamin and mineral use: A rapid review of meta-analyses on health outcomes.. Ageing Res Rev. 2026. PMID 41308839. DOI 10.1016/j.arr.2025.102965. (abstract)
- Wilson RD, Wilson RD, Audibert F et al.. Pre-conception Folic Acid and Multivitamin Supplementation for the Primary and Secondary Prevention of Neural Tube Defects and Other Folic Acid-Sensitive Congenital Anomalies.. J Obstet Gynaecol Can. 2015. PMID 26334606. DOI 10.1016/s1701-2163(15)30230-9. (abstract)
- Zamil DH, Burns EK, Perez-Sanchez A et al.. Risk of Birth Defects From Vitamin A "Acne Supplements" Sold Online.. Dermatol Pract Concept. 2021. PMID 34123566. DOI 10.5826/dpc.1103a75. (abstract)
- . FDA: Daily Value on the Nutrition and Supplement Facts Labels (content current as of 5 March 2024). . . (full-text)
- . FDA: Information for Consumers on Using Dietary Supplements (content current as of 21 October 2022). . . (full-text)
- . MedlinePlus Health Topic: Pregnancy and Nutrition. . . (full-text)
- . MedlinePlus Drug Information: Prenatal Vitamins (last revised 15 March 2025). . . (full-text)
- . NHS: Vitamins and minerals, B vitamins and folic acid (page last reviewed 3 August 2020). . . (full-text)
- . NHS: Vitamins and minerals, Iodine (page last reviewed 3 August 2020). . . (full-text)
- . NHS: Vitamins and minerals, Iron (page last reviewed 3 August 2020). . . (full-text)
- . NHS: Pregnancy vitamins and supplements (page last reviewed 3 June 2026). . . (full-text)
- . NHS: Vitamins and minerals, Vitamin A (page last reviewed 3 August 2020). . . (full-text)
- . NIH Office of Dietary Supplements: Folate fact sheet for health professionals. . . (not-read)
- . PubMed search record: "prenatal vitamin gummy versus tablet" (2026-10-26). . . (search-record)
Where to buy
Check the label first. Whatever you buy, look for these:
- The amount of the active ingredient per serving, not just the front-label claim
- A third-party testing mark (USP, NSF or ConsumerLab)
- Other ingredients and allergens
- Ask a pharmacist about interactions with your medicines
Talk to a pharmacist or doctor before you start any supplement, especially if you take medicines. See the Safety tab for interactions.
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