Randomized, Controlled Trial of Prenatal Zinc Supplementation and Fetal Bone Growth

Abstract

Zinc deficiency in pregnancy probably is common all over the world but especially in developing countries and where women eat a diet based on cereals, vegetables, and legumes. It has been estimated that approximately 80% of pregnant women worldwide may consume an inadequate amount of zinc. Whether maternal zinc deficiency impedes fetal growth is not clear. This double-blind, randomized trial related maternal zinc status during pregnancy to fetal growth as measured sonographically. The subjects were 242 Peruvian women living in an impoverished area of Lima. At 10 to 16 weeks gestation, they were assigned to receive daily supplements of 60 mg iron and 250 μg folic acid with or without 25 mg of zinc. Fetal head circumference, biparietal diameter, abdominal circumference, and length of the femoral diaphysis were measured every 4 weeks from 20 to 38 weeks gestation. Compliance with taking supplements was estimated at 87%. Women took their assigned supplements a median of 6 days a week. There were no significant differences between the 2 groups in duration of pregnancy, neonatal size, head circumference, biparietal diameter, or abdominal circumference. Femoral diaphysial length, however, was greater in zinc-supplemented women than in those taking only iron and folic acid. The effect of zinc on femoral length appeared to increase with advancing gestational age. It approximated one fourth of the reference standard deviation. The positive effect of supplemental zinc on fetal femoral length observed in this study is consistent with experimental animal and in vitro studies that have demonstrated a stimulatory effect of zinc on bone growth. Previous studies also have shown an adverse effect of maternal zinc deficiency on bone growth and fetal bone metabolism. The present findings endorse the use of zinc supplements when dietary zinc intake is inadequate.