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

BACKGROUND: The need for prophylactic iron during pregnancy is uncertain. OBJECTIVE: We tested the hypothesis that administration of a daily iron supplement from enrollment to 28 wk of gestation to initially iron-replete, nonanemic pregnant women would reduce the prevalence of anemia at 28 wk and increase birth weight. DESIGN: Between June 1995 and September 1998, 513 low-income pregnant women in Cleveland were enrolled in the study before 20 wk of gestation. Of these, 275 had a hemoglobin concentration >/= 110 g/L and a ferritin concentration >/= 20 micro g/L and were randomly assigned to receive a monthly supply of capsules containing either 30 mg Fe as ferrous sulfate or placebo until 28 wk of gestation. At 28 and 38 wk of gestation, women with a ferritin concentration of 12 to < 20 micro g/L or < 12 micro g/L received 30 and 60 mg Fe/d, respectively, regardless of initial assignment. Almost all the women received some supplemental iron during pregnancy. We obtained infant birth weight and gestational age at delivery for 117 and 96 of the 146 and 129 women randomly assigned to receive iron and placebo, respectively. RESULTS: Compared with placebo, iron supplementation from enrollment to 28 wk of gestation did not significantly affect the overall prevalence of anemia or the incidence of preterm births but led to a significantly higher mean (+/- SD) birth weight (206 +/- 565 g; P = 0.010), a significantly lower incidence of low-birth-weight infants (4% compared with 17%; P = 0.003), and a significantly lower incidence of preterm low-birth-weight infants (3% compared with 10%; P = 0.017). CONCLUSION: Prenatal prophylactic iron supplementation deserves further examination as a measure to improve birth weight and potentially reduce health care costs.