Effects of iron supplementation in nonanemic pregnant women, infants, and young children on the mental performance and psychomotor development of children: a systematic review of randomized controlled trials.

Systematic review of randomized controlled trials in nonanemic pregnant women and nonanemic healthy infants and young children up to 3 years of age. Included studies were conducted in Canada, Indonesia, the United Kingdom, Turkey, and Australia, with outcomes focused on mental development, psychomotor development, IQ, and behavior.

Iron supplementation was evaluated in several RCTs using different oral regimens, including ferrous sulfate 7.5 mg/d, ferrous sulfate 10 mg/d, iron-fortified formula (12.8 mg/L, 1.2 mg/L, or 0.9-1.1 mg/L comparator formulas), and prenatal iron 20 mg/d. Interventions were given to nonanemic pregnant women or to healthy infants and young children, with follow-up extending to about 12 to 18 months in most child studies and to later childhood for some prenatal follow-up.

Overall, iron supplementation showed a possible benefit for infant psychomotor development but not for mental development, and prenatal supplementation did not improve child IQ or behavior. In pooled infant analyses at about 12 months, mental development was not significantly different (WMD 1.66; 95% CI, -0.14 to 3.47), whereas psychomotor development favored iron (WMD 4.21; 95% CI, 2.31 to 6.12; n = 561 across 3 RCTs). In one prenatal trial, abnormal behavior was more common in the iron group (RR 1.97; 95% CI, 1.03 to 3.80; P = 0.037), while another found no significant behavior or temperament differences. The authors concluded that evidence is limited and does not support a clear cognitive benefit in nonanemic populations.

The evidence base was small and heterogeneous, with different iron forms, doses, ages, and outcome measures across trials. Follow-up was generally short for infant studies, and prenatal findings were based on limited numbers of studies and outcomes. Generalizability is constrained because participants were nonanemic and drawn from specific countries and settings.