title: The impact of duration of labor induction on cesarean rate.
abstract: OBJECTIVE
  We sought to determine maternal factors that influence success of labor induction and whether the probability of cesarean delivery changed with time during induction.
  
  
  METHODS
  We performed a retrospective cohort study of 1650 singleton pregnancies induced at a gestation of 37 weeks or longer, with birthweights of 2500 g or greater, and without congenital anomalies. We used multivariate logistic regression to calculate odds ratios for cesarean.
  
  
  RESULTS
  Nulliparity (odds ratio [OR] 7.8, 95% confidence interval [CI] 5.7 to 11), hypertension (OR 1.4, 95% CI 1.1 to 1.8), diabetes (OR 2.2, 95% CI 1.6 to 3.1), maternal age 28.8 years old or older (OR 1.3, 95% CI 1.2 to 1.4), and birthweight of 3441 g or greater (OR 1.6, 95% CI 1.2 to 2.0) were significantly associated with cesarean. Cesarean risk increased linearly with time by an average of 3.8% per 6 hours.
  
  
  CONCLUSIONS
  Risk of cesarean increases over the duration of induction but does not reach clinical certainty. Cesarean probability is greater with nulliparity, hypertension, diabetes, older maternal age, or higher birthweight. Inductions without stated indications may not carry an increased risk of cesarean.
authors.affiliation: College of Physicians and Surgeons, Columbia University, New York, NY, USA.
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Michelson
authors.forename: Darcy B
authors.initials: DB
authors.lastname: Carr
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Easterling
mesh_terms: D000328:Adult; D002585:Cesarean Section / Q000706:statistics & numerical data*; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D007751:Labor, Induced; D016017:Odds Ratio; D011247:Pregnancy; D011336:Probability; D012189:Retrospective Studies; D012307:Risk Factors; D013997:Time Factors