THE EFFECT OF ZINC SUPPLEMENTATION ON PREGNANCY OUTCOME

Objective.-To evaluate whether zinc supplementation during pregnancy i s associated with an increase in birth weight. Design.-A randomized do uble-blind placebo-controlled trial. Setting.-Outpatient clinic and de livery service at the University of Alabama at Birmingham. Patients.-F ive hundred eighty medically indigent but otherwise healthy African-Am erican pregnant women with plasma zinc levels below the median at enro llment in prenatal care, randomized at 19 weeks' gestational age. Wome n were subdivided by the population median body mass index of 26 kg/m( 2) into two groups for additional analyses. Intervention.-Women who we re taking a non-zinc-containing prenatal multivitamin/mineral tablet w ere randomized to receive either a daily dose of 25 mg of zinc or a pl acebo until delivery. Main Outcome Measures.-Birth weight, gestational age at birth, and head circumference at birth. Results.-In all women, infants in the zinc supplement group had a significantly greater birt h weight (126 g, P=.03) and head circumference (0.4 cm, P=.02) than in fants in the placebo group. In women with a body mass index less than 26 kg/m(2), zinc supplementation was associated with a 248-g higher in fant birth weight (P=.005) and a 0.7-cm larger infant head circumferen ce (P=.007). Plasma zinc concentrations were significantly higher in t he zinc supplement group. Conclusions.-Daily zinc supplementation in w omen with relatively low plasma zinc concentrations in early pregnancy is associated with greater infant birth weights and head circumferenc es, with the effect occurring predominantly in women with a body mass index less than 26 kg/m(2).