title: Secondary analysis of the use of transdermal nitroglycerin for preterm labor.
abstract: 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.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  We hypothesize that GTN has a gestational age-dependent reduction in neonatal outcomes as a result of pregnancy prolongation and corticosteroid administration.
authors.affiliation: Department of Obstetrics and Gynecology, Queen's Perinatal Research Unit, Kingston General Hospital, Queen's University, Kingston, ON, Canada. gns@queensu.ca.
authors.forename: Graeme N
authors.initials: GN
authors.lastname: Smith
authors.forename: Yanfang
authors.initials: Y
authors.lastname: Guo
authors.forename: Shi Wu
authors.initials: SW
authors.lastname: Wen
authors.forename: Mark C
authors.initials: MC
authors.lastname: Walker
mesh_terms: D000279:Administration, Cutaneous; D000328:Adult; D016001:Confidence Intervals; D036861:Delivery, Obstetric / Q000379:methods; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004334:Drug Administration Schedule; D005260:Female; D005500:Follow-Up Studies; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D008423:Maternal Age; D005996:Nitroglycerin / Q000008:administration & dosage*; D007752:Obstetric Labor, Premature / Q000188:drug therapy* / Q000517:prevention & control; D011247:Pregnancy; D011256:Pregnancy Outcome; D012016:Reference Values; D047929:Term Birth; D016896:Treatment Outcome; D055815:Young Adult
chemical_list: D005996:Nitroglycerin