Effect of iron supplementation during pregnancy on the intelligence quotient and behavior of children at 4 y of age: Long-term follow-up of a randomized controlled trial

Background: Iron supplements are often prescribed during pregnancy despite the lack of intervention trials that have assessed the effects of supplementation in pregnancy on childhood development. Objective: The objective was to determine whether iron supplementation during pregnancy influences childhood intelligence quotient (IQ) in an industrialized country. Design: Pregnant women (n = 430) were randomly allocated to receive iron (20 mg/d) or placebo from 20 wk gestation until delivery, and thewomenand their children were followed up over the long term (4 y). Seventy percent of these families participated in the follow-up. The proportion of women with iron deficiency anemia at the end of pregnancy was 1% (2 of 146) in the iron group and 11% (15 of 141) in the placebo group. The primary outcome was the IQ of the children at 4 y of age, as assessed by the Stanford-Binet Intelligence Scale. Secondary outcomes included child behavior and the general health of the mothers. Results: The mean IQ was not significantly different (P = 0.980) between the children of the iron-supplemented mothers (109 ± 11; n = 153) and the children of the mothers in the placebo group (109 ± 11; n = 149). However, the percentage of children with an abnormal behavior score was higher in the iron group (24 of 151, or 16%) than in the placebo group (12 of 149, or 8%); the relative risk was 1.97 (95% CI: 1.03, 3.80; P = 0.037). There was no significant difference in the health of the mothers between groups, as assessed by the SF-36 Health Survey. Conclusions: Prenatal iron supplementation that reduces the incidence of iron deficiency anemia from 11% to1%has no effect on the IQ of the offspring at 4 y of age.