Effect of Zinc Supplement on Prevention of PPROM and Improvement of some Pregnancy Outcomes in Pregnant Women with a History of PPROM: A Randomized Double -Blind Controlled Trial

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Background Preterm premature rupture of membrane (PPROM) prior to 37 weeks’ gestation is among the most common obstetrics problems, which is associated with prenatal mortality and several maternal and neonatal complications. History of PPROM is a risk factor for recurrence. Zinc has an important effect on the strength of membranes by affecting collagen [tensile] strength - a substance with immunity mechanism and antioxidant properties.Objectives This study was conducted to investigate the effect of zinc supplement on the prevention of PPROM and improvement of some pregnancy outcomes in pregnant women with a history of PPROM during the second trimester and the early third trimester.Methods In this randomized, double-blind, controlled clinical trial, 108 healthy pregnant women (at gestational age of 16 - 30 weeks) with a history of PPROM and singleton pregnancy were selected by convenience sampling method in the Midwifery Clinic of Shahid Akbarabadi hospital in Tehran, Iran, between 2014 and 2015. They were then divided into two groups of placebo and zinc sulfate tablet (40 mg) recipient using randomized block design. In total, 92 subjects completed the study. The frequency of PPROM was regarded as the primary outcome, and frequency of PROM, average gestational age at birth, average birth weight, and average head circumference were considered as the secondary outcomes. The statistical analysis was based on intent-to-treat principle.Results There was no between-groups difference in terms of demographic and pregnancy specifications. Results showed no significant between-groups (zinc versus placebo recipient) difference (P > 0.05) in terms of the frequency of preterm pregnancy (22% versus 33.3%), frequency of PPROM (4.9% versus 11.8%), frequency of PROM (14.6% versus 17.6%), average birth weight (3192.17 g versus 3080.52 g), average gestational age at birth (38.2 weeks versus 37.2 weeks), and average head circumference at birth (34.63 cm versus 34.81 cm).Conclusions According to the results, daily intake of zinc sulfate (40 mg) by pregnant women with a history of PPROM does not contribute to the prevention of PPROM and PROM and improvement of average gestational age at birth and anthropometric measurements.