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Iron in pregnancy

Goal: What trials and WHO used to prevent anemia and iron deficiency in pregnancy.

Each protocol describes what studies used, for one goal or for one group of people. It is not advice for you: talk to a doctor before you start a supplement.

Updated 9 Nov 2026
Dose

WHO recommends 30 to 60 mg of elemental iron a day with 400 µg of folic acid.[1] The US recommended intake in pregnancy is 27 mg a day.[2]

Form

Iron by mouth. 60 mg of elemental iron is in 300 mg of ferrous sulfate heptahydrate, 180 mg of ferrous fumarate or 500 mg of ferrous gluconate.[1]

When to take

Every day.[1]

How long

During pregnancy.[3]

What studies found

A 2024 Cochrane review of 57 trials with 48,971 women found that daily iron may reduce anemia at term (4.0% against 7.4%, low certainty) and probably reduces low birthweight (5.2% against 6.1%). It probably makes little or no difference to preterm birth.[3]

Ask a doctor first

The US upper limit in pregnancy is 45 mg a day, and EFSA names 40 mg a day a safe level.[2][4] In 7 trials with 1,028 pregnant women, ferrous sulfate raised the odds of stomach and gut side effects about 3 times.[5]

US expert groups disagree on routine iron for pregnant women without symptoms. The Dietary Guidelines for Americans advise taking iron when an obstetrician or other health care provider recommends it.[2]

References

  1. Daily iron and folic acid supplementation during pregnancy. World Health Organization, 2024. www.who.int
  2. Iron: Fact Sheet for Health Professionals. NIH Office of Dietary Supplements. ods.od.nih.gov
  3. Daily oral iron supplementation during pregnancy. Finkelstein JL, Cuthbert A, Weeks J, Venkatramanan S, Larvie DY, De-Regil LM, et al. Cochrane Database Syst Rev, 2024. PMID 39145520
  4. Scientific opinion on the tolerable upper intake level for iron. EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) European Food Safety Authority, 2024. efsa.onlinelibrary.wiley.com
  5. Ferrous sulfate supplementation causes significant gastrointestinal side-effects in adults: a systematic review and meta-analysis. Tolkien Z, Stecher L, Mander AP, Pereira DI, Powell JJ PLoS One, 2015. PMID 25700159