Zinc Supplementation during Pregnancy: A Randomized Controlled Trial

Zinc deficiency during pregnancy has been related to adverse pregnancy outcomes. However, the results of zinc-supplementation trials have not been consistent in improvement of pregnancies outcomes. This study was undertaken to investigate whether zinc supplementation was associated with pregnancy complications in Iranian women during the last 2 trimesters. It also assessed the anthropometric measurements of infants at birth. A double-blind placebo-controlled trial was conducted in Ardabil Province located in northwest of Iran. One-hundred ninty-six pregnant women between 16-20 weeks of gestation were recruited from urban healthcare centres. These women had no evidence of hypertension, diabetes, renal disease, history of prematurity, premature rupture of membranes (PROM) or low birth weight (LBW) infants. They were randomly assigned to receive zinc (50 mg daily) or placebo until delivery. Basic information was collected on socioeconomic status, reproductive and disease histories before randomization. The subjects were monthly followed during pregnancy and maternal complications were carefully recorded. The weight, length and head circumference of each infant was measured within 24h of birth. Of the 196 women, 17 were excluded from the study (9 in the zinc group and 8 in the placebo group, NS). The supplementation had no significant effect on prematurity, preeclampcia, PROM and stillbirth as well as gestational age, infant length and head circumference. The incidence of low birth weight was significantly lower in those under Zinc than placebo ( p = 0.01). Meanwhile, pregnancy-induced hypertension and intrauterine growth retardation (IUGR) were observed only in the placebo group. The birth weight was also higher in the zinc group than that in the placebo group ( p = 0.03). Supplementation with 50mg elemental zinc during pregnancy improved birth weight but did not reduce maternal complications.