Randomized double-blind placebo-controlled trial of transdermal nitroglycerin for preterm labor.

Author(s): Smith GN, Walker MC, Ohlsson A, O'Brien K, Windrim R, Canadian Preterm Labour Nitroglycerin Trial Group

Affiliation(s): Queen's Perinatal Research Unit, Department of Obstetrics and Gynecology, Kingston General Hospital, Queen's University, Kingston, Ontario, Canada. gns@post.queensu.ca

Publication date & source: 2007-01, Am J Obstet Gynecol., 196(1):37.e1-8.

Publication type: Research Support, Non-U.S. Gov't

OBJECTIVE: Despite advances in perinatal medicine, the incidence of preterm birth continues to increase. The primary goal of tocolytic therapy is to reduce neonatal morbidity and mortality. While studies have demonstrated a prolongation of pregnancy, no tocolytic has been shown to improve neonatal outcomes. The objective of this randomized placebo-controlled trial was to determine the effect of transdermal nitroglycerin on neonatal outcomes in women who present in preterm labor. STUDY DESIGN: We randomized 153 women in labor between 24 and 32 weeks to receive either transdermal nitroglycerin or placebo patches. The primary outcome was a composite of neonatal morbidity (chronic lung disease, intraventricular hemorrhage, periventricular leukomalacia, necrotizing enterocolitis) and mortality. Secondary outcomes included birth within 48 hours, birth before 28, 34, and 37 weeks, number of doses of antenatal corticosteroids received, side effects, and adverse events. RESULTS: Infants born to transdermal nitroglycerin treated mothers (n = 74) had a statistically significantly reduced composite outcome compared to placebo treated mothers (n = 79) (relative risk 0.29 [95% confidence interval 0.08, 1.00] [p = 0.048]; risk difference -0.10 [95% confidence interval -0.19, -0.01); number needed to treat 10 [95% confidence interval 5, 100]). Birth prior to 28 weeks was reduced (relative risk 0.50, 95% confidence interval 0.23, 1.09). Transdermal nitroglycerin caused significantly more maternal side effects (relative risk 1.41, 95% confidence interval 1.06, 1.86). CONCLUSION: Transdermal nitroglycerin may reduce neonatal morbidity and mortality as a result of decreased risk of birth before 28 weeks.