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Prenatal Multivitamin

One of the few supplements with genuinely strong evidence — but the benefit comes from a few specific nutrients (folic acid, iodine, iron, choline, DHA), not from having fifty ingredients on the label. Buying on nutrient content rather than brand story is what matters.

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What the science says

  • Folic acid before and in early pregnancy prevents neural tube defects Strong evidence

    The Cochrane review of periconceptional folate supplementation (5 trials, 6,708 births) found a risk ratio of 0.31 (95% CI 0.17-0.58) for neural tube defects — roughly a 70% reduction — rated high-quality evidence, with a protective effect against recurrence of RR 0.34. Doses of 400 µg/day and above worked; the neural tube closes by about day 28, so supplementation must start before conception.

  • A full multiple-micronutrient prenatal beats iron and folic acid alone Strong evidence

    The Cochrane review of multiple-micronutrient supplementation in pregnancy (20 trials, 141,849 women) found MMN reduced low birthweight (RR 0.88, 95% CI 0.85-0.91, high-quality evidence) and small-for-gestational-age births (RR 0.92, 0.88-0.97), and probably reduced very preterm birth (RR 0.81, 0.71-0.93). It showed no difference in perinatal, neonatal or maternal mortality. Most of these trials were in low- and middle-income settings, so the size of the benefit in a well-nourished population is likely smaller.

  • Any product labelled 'prenatal' contains what you need Moderate evidence

    Nutrient content varies substantially across prenatal products, and analyses of prescription versus over-the-counter prenatals have found meaningful differences in which nutrients are included — iodine in particular is missing from many products despite professional recommendations of 150 µg/day during pregnancy and lactation. Choline is the other common gap: the adequate intake is 450 mg/day in pregnancy and most prenatals supply a small fraction of it.

  • More vitamin A is better for the baby Strong evidence

    The opposite: preformed vitamin A (retinol/retinyl palmitate) is teratogenic above roughly 10,000 IU/day, and prenatal products should supply vitamin A predominantly as beta carotene, which is not associated with birth defects. Check the form on the Supplement Facts panel, and avoid stacking a prenatal with cod liver oil or a separate retinol supplement.

Dosage & safety

Studied doseFolic acid 400-800 µg/day starting at least one month before conception (4-5 mg/day if there is a prior NTD-affected pregnancy or certain risk factors, on medical advice); iodine 150 µg/day; iron 27 mg/day during pregnancy; vitamin D 600 IU/day minimum; calcium 1,000 mg/day from diet plus supplement; choline 450 mg/day (most prenatals supply 0-55 mg, so a separate source is usually needed); DHA 200-300 mg/day. Vitamin A should come mostly as beta carotene, capped at about 770 µg RAE/day of preformed retinol. Continue through breastfeeding.
SafetyIron is the most common tolerability problem — constipation, nausea and dark stools; taking it with vitamin C and away from calcium and coffee helps, and iron-containing bottles must be stored out of children's reach because iron overdose is a leading cause of fatal poisoning in young children. Avoid high-dose preformed vitamin A. Do not add extra herbs to a prenatal regimen without obstetric advice; many botanicals are untested or contraindicated in pregnancy. Gummy prenatals almost never contain iron and often omit iodine, so check the label rather than assuming coverage. Prenatal supplements complement but do not replace prenatal care.

How to take it

TimingOnce daily at whatever time you will reliably remember, with folic acid starting at least a month before conception and continuing through breastfeeding.
With food?Take it with food — iron on an empty stomach is what causes most of the nausea.
Worth knowingMost prenatals supply almost no choline, and gummies usually contain no iron and often no iodine, so read the panel rather than assuming coverage.

Interactions

With medications

  • levothyroxine

    The calcium and iron in a prenatal bind levothyroxine and substantially cut its absorption. take levothyroxine on an empty stomach and separate it from the prenatal by at least 4 hours

  • tetracycline and quinolone antibiotics

    Calcium, iron, magnesium and zinc chelate these antibiotics and reduce their absorption. separate the antibiotic from the prenatal by at least 2-4 hours

With other supplements

  • calcium supplements

    Calcium competes directly with iron for absorption. take extra calcium at a different meal from the iron-containing prenatal

  • additional vitamin A or cod liver oil

    Preformed retinol is teratogenic above about 770 µg RAE/day and stacks quickly across products. do not add retinol-containing supplements during pregnancy

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Do prenatal vitamins prevent birth defects?

For neural tube defects, yes, and the evidence is strong: folic acid at 400 mcg/day or more around conception cut neural tube defects by roughly 70% in a Cochrane review. A prenatal multivitamin must start before conception, because the neural tube closes by about day 28.

When should I start taking a prenatal multivitamin?

Start a prenatal multivitamin with folic acid at least one month before conception and continue through breastfeeding. Take it once daily with food, since iron on an empty stomach causes most of the nausea.

What should a good prenatal vitamin contain?

Look for folic acid 400-800 mcg, iodine 150 mcg, iron 27 mg, vitamin D at least 600 IU and DHA 200-300 mg, with vitamin A mostly as beta carotene. Most prenatal multivitamins supply little choline against the 450 mg/day target, and gummies often lack iron and iodine.

Can I take a prenatal vitamin with levothyroxine?

The calcium and iron in a prenatal multivitamin substantially cut levothyroxine absorption, so take levothyroxine on an empty stomach and separate it from the prenatal by at least 4 hours.

Scientific references

Where to buy

Thorne, Basic Prenatal, 90 Capsules

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