Objective: This study was undertaken to assess the effectiveness of glyceryl trinitrate (GTN) patches in comparison with β2 sympathomimetics (β2) for the treatment of preterm labor. Study design: A multicenter, multinational, randomized controlled trial was conducted in tertiary referral teaching hospitals. Women in threatened preterm labor with positive fetal fibronectin or ruptured membranes between 24 and 35 weeks' gestation were recruited and randomly assigned to either β2 or GTN with rescue β2 tocolysis if moderate-to-strong contractions persisted at 2 hours. Obstetric and neonatal outcomes were assessed. Results: Two hundred thity-eight women were recruited and randomly assigned, 117 to β2 and 121 to GTN. On a strict intention-to-treat basis, there was no significant difference in the time to delivery using Kaplan-Meier curves (P = .451). At 2 hours, 27% of women receiving β2 had moderate or stronger contractions compared with 53% in the GTN group (P < .001). This led to 35% of women in the GTN group receiving rescue treatment. If delivery or requirement for β2 rescue are regarded as treatment failure, then a significant difference was observed between the 2 arms (P = .0032). There were no significant differences in neonatal outcomes. Conclusion: GTN is a less efficacious tocolytic compared with β2 sympathomimetics.
American Journal of Obstetrics and Gynecology Vol. 191, Issue 3, p. 683-90