Secondary analysis of the use of transdermal nitroglycerin for preterm labor.

Objective: This secondary analysis of a randomized placebo-controlled trial was to hypothesize on mechanisms for the improved neonatal outcomes with the use of nitroglycerin (GTN) for preterm labor. Study Design: Women in the original trial who delivered at term were excluded. A composite of severe neonatal outcomes, gestational age at delivery, and corticosteroid use in addition to Kaplan-Meier survival analysis to assess time from randomization to delivery were examined. Results: A decrease in composite neonatal outcome (relative risk, 0.21; 95% confidence interval, 0.05–0.81; P = .018) with GTN (n = 39) compared with placebo (n = 38) was primarily due to a 23 day prolongation of pregnancy (P = .019) and a trend (P = .04) toward completing a course of corticosteroids in the subgroup randomized prior to 28 weeks'' gestation. Conclusion: We hypothesize that GTN has a gestational age–dependent reduction in neonatal outcomes as a result of pregnancy prolongation and corticosteroid administration. [Copyright &y& Elsevier]