Frequency of Preterm Delivery with and Without Zinc Supplementation in Pregnant Women Presenting In the Third Trimester: A Prospective Comparative Study

Abstract

Objective: To compare the frequency of preterm delivery among pregnant women receiving zinc supplementation and those without supplementation.

Study Design: Prospective comparative cohort study.

Place and Duration of Study: Tertiary care hospital, Pakistan, from 1 January 2026 to 30 June 2026.

Methodology: A total of 618 pregnant women with singleton pregnancies at 28–34 weeks of gestation were enrolled through consecutive sampling. Participants were categorized into zinc supplementation (20 mg/day) and non-supplementation groups. Following losses to follow-up, 557 women (282 receiving zinc and 275 without zinc) were analyzed. Preterm delivery was defined as childbirth before 37 completed weeks. Associations were assessed using comparative statistical tests and multivariable logistic regression adjusting for maternal and obstetric factors.

Results: The mean maternal age was 28.0 ± 4.8 years in the zinc group and 27.8 ± 4.4 years in the non-zinc group. Preterm delivery occurred in 25 (8.9%) women receiving zinc compared with 39 (14.2%) without supplementation, representing an absolute difference of 5.3 percentage points (RR 0.63, 95% CI 0.39–1.00). The unadjusted association was borderline and sensitive to statistical testing (Pearson p = 0.049; Fisher p = 0.062). After adjustment for maternal and obstetric factors, zinc supplementation was associated with lower odds of preterm delivery (adjusted OR 0.51, 95% CI 0.30–0.89; p = 0.018). Previous preterm birth was independently associated with increased risk (adjusted OR 3.13, 95% CI 1.50–6.51; p = 0.002).

Conclusion: Antenatal zinc supplementation was associated with a lower frequency of preterm delivery after adjustment for maternal and obstetric factors. Larger randomized studies are needed to establish its preventive effectiveness.