The effect of zinc supplementation on pregnancy outcome: a randomized controlled trial

Objectives: This study aimed to evaluate the impact of prenatal zinc supplementation on pregnancy outcomes. Methods: A randomized controlled trial with equal randomization (1: 1) was conducted on 540 pregnant women in Rasht, Iran from January 2010 to January 2012. Participants were randomly assigned to receive a daily supplement including 400-mu g folic acid and 30-mg ferrous sulfate, with or without 15-mg zinc sulfate from the 16th week of gestation until delivery. Results: Mean difference of birth weight between the two groups was not significantly different (3262 +/- 390 g in the zinc, 3272 +/- 403 g in the no-zinc groups) (p = 0.780). There were no significant differences between the two groups in terms of means of head circumference (p = 0.999), length (p = 0.848), and gestational age at birth (p = 0.057) incidences of low birth weight (p = 0.863), macrosomia (p = 0.642), and the Apgar score >7 at 5 min (p = 0.999), incidences of preterm delivery (p = 0.999), pre-eclampsia (p = 0.835), premature rupture of membranes (p = 0.630), and spontaneous abortion (p = 0.772). Abruption of placenta, amnionitis, stillbirth, and intrauterine death were not observed. Conclusion: Based on our findings, 15-mg zinc supplementation daily from 16 weeks of pregnancy until delivery cannot improve pregnancy outcomes.