The effect of zinc supplementation on pregnancy outcomes: a double-blind, randomised controlled trial, Egypt

Double-blind randomized controlled trial in zinc-deficient pregnant women attending antenatal care in Alexandria, Egypt, with enrolment around 15 weeks' gestation. In the active arms, 225 women were randomized and 198 completed in the zinc-alone group, and 227 were randomized and 200 completed in the zinc-plus-multivitamin group; the trial compared these regimens with placebo.

Zinc-alone arm: 30 mg zinc sulfate orally once daily after meals from enrolment until delivery. Zinc-plus-multivitamin arm: 30 mg zinc sulfate orally once daily after meals plus a multivitamin capsule containing vitamin B1, vitamin B6, vitamin E, vitamin D3, and vitamin C, taken daily until delivery.

Zinc supplementation improved several obstetric and early neonatal outcomes in zinc-deficient pregnant women, with the zinc-alone regimen generally showing the stronger effect; birth weight did not differ meaningfully across groups. Second-and third-stage complications were reduced versus placebo, with RR 0.43, 95% CI 0.31, 0.60 for zinc alone and RR 0.54, 95% CI 0.40, 0.73 for zinc plus multivitamins. Preterm delivery occurred in 21 (10.6%) placebo, 2 (1%) zinc, and 4 (2%) zinc plus multivitamin participants; reported RR 0.012, 95% CI 0.036, 0.377 for zinc and RR 0.268, 95% CI 0.119, 0.603 for zinc plus multivitamins versus placebo. Early neonatal morbidity was also lower, with RR 0.23, 95% CI 0.15, 0.35 for zinc and RR 0.25, 95% CI 0.16, 0.37 for zinc plus multivitamins. Second serum zinc increased to 75.07 mg/dl with zinc and 70.35 mg/dl with zinc plus multivitamins versus 60.68 mg/dl with placebo.

The trial was conducted in zinc-deficient pregnant women from one city in Egypt, so generalizability is limited. Some attrition occurred between randomization and completion, and dietary assessment was available only in a subsample of 100 women. Follow-up was limited to delivery and early neonatal outcomes, so longer-term maternal and infant effects were not assessed.