Objective: The hypothesis that daily use of a prenatal supplement with iron from enrollment to third trimester to initially iron-replete, nonanemic pregnant women would reduce third-trimester anemia and improve birth outcomes was tested.
Study design: Eight hundred sixty-seven women in Raleigh, North Carolina, who were at < 20 weeks of gestation were enrolled; 429 of these women had hemoglobin levels of > or = 110 g/L and ferritin levels of > or = 40 microg/L and were assigned randomly to receive prenatal supplements with 30 mg of iron as ferrous sulfate (n = 218 women) or 0 mg of iron (n = 211 women) until 26 to 29 weeks of gestation. Intent-to-treat analysis was used for the outcomes of third-trimester iron status, birth weight, preterm birth, and small-for-gestational age.
Results: Mean birth weight was higher by 108 g (P = .03), and the incidence of preterm delivery was lower (8% vs 14%; P = .05) in the 30-mg group compared with the control group, respectively. Iron supplementation did not affect the prevalence of small-for-gestational age infants or third-trimester iron status.
Conclusion: Prophylactic iron supplementation that is begun early in pregnancy among low income women in the United States may have benefits beyond the reduction of iron deficiency anemia during pregnancy.