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 the women and 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% to 1% has no effect on the IQ of the offspring at 4 y of age.