A randomized, placebo-controlled trial of the effect of zinc supplementation during pregnancy on pregnancy outcome in Bangladeshi urban poor.

Randomized, double-blind, placebo-controlled trial in pregnant women from the urban slums of Dhaka, Bangladesh. Women were enrolled at 12 to 16 weeks gestation, were of very low socioeconomic status, and had no major medical risk factors for abnormal birth weight; they were followed through delivery.

Pregnant women in the active arm received 30 mg elemental zinc per day as oral zinc acetate tablets, taken daily from enrollment in the last two trimesters until delivery. Tablets were supplied weekly and were to be taken between meals and not with other vitamin or mineral supplements.

Zinc supplementation did not improve pregnancy or birth outcomes. In the zinc group, mean birth weight was 2513 ± 390 g versus 2554 ± 393 g with placebo, and there were no significant differences in gestational age, infant length, head circumference, chest circumference, or MUAC. Low birth weight, prematurity, and small for gestational age rates were also similar between groups, and serum zinc at 7 months gestation was 15.9 ± 4.4 mol/L versus 15.2 ± 4.3 mol/L, P = 0.065. The authors concluded that zinc alone is unlikely to reduce low birth weight in this population.

A substantial number of participants were lost before delivery, and birth-weight analyses included fewer singleton infants than were randomized. The trial was conducted in a specific urban poor population in Dhaka, limiting generalizability, and the results do not exclude the possibility of small effects that this sample size could miss.