Iron supplementation during pregnancy, anemia, and birth weight: a randomized controlled trial.

Randomized controlled trial in low-income pregnant women enrolled in WIC in Cleveland, United States, before 20 weeks of gestation. Participants were initially iron-replete and nonanemic at baseline (hemoglobin ≥110 g/L and ferritin ≥20 g/L) and were randomized to iron or placebo.

Daily oral iron supplementation provided 30 mg Fe/day as ferrous sulfate from enrollment until 28 weeks of gestation, compared with placebo. At 28 weeks, participants without iron stores or with depleted iron stores were prescribed 60 mg Fe/day.

Daily iron supplementation did not significantly reduce anemia at 28 weeks, but it was associated with better birth outcomes. At 28 weeks, anemia was 19.8% with iron versus 26.7% with placebo, while birth weight was higher with iron (3277 ± 501 g vs 3072 ± 635 g) and low birth weight was lower (4% vs 16.7%). Preterm delivery with low birth weight was also lower (2.6% vs 10.4%), and the authors concluded that prophylactic prenatal iron deserves further study for improving birth weight and possibly reducing health care costs.

Outcome follow-up was incomplete for both iron status and birth outcomes, with analyses limited to smaller subsets of the randomized groups. The trial was conducted in a single low-income WIC population of initially iron-replete, nonanemic women, which limits generalizability. The intervention period was relatively short and the study was not powered to definitively establish all maternal and neonatal benefits.