title: Risk of cesarean delivery with elective induction of labor at term in nulliparous women.
abstract: OBJECTIVE
  To quantify the risk of cesarean delivery associated with elective induction of labor in nulliparous women at term.
  
  
  METHODS
  We performed a cohort study on a major urban obstetric service that serves predominantly private obstetric practices. All term, nulliparous women with vertex, singleton gestations who labored during an 8-month period (n = 1561) were divided into three groups: spontaneous labor, elective induction, and medical induction. The risk of cesarean delivery in the induction groups was determined using stepwise logistic regression to control for potential confounding factors.
  
  
  RESULTS
  Women experiencing spontaneous labor had a 7.8% cesarean delivery rate, whereas women undergoing elective labor induction had a 17.5% cesarean delivery rate (adjusted odds ratio [OR] 1.89; 95% confidence interval [CI] 1.12, 3.18) and women undergoing medically indicated labor induction had a 17.7% cesarean delivery rate (OR 1.69; 95% CI 1.13, 2.54). Other variables that remained significant risk factors for cesarean delivery in the model included: epidural placement at less than 4 cm dilatation (OR 4.66; 95% CI 2.25, 9.66), epidural placement after 4 cm dilatation (OR 2.18; 95% CI 1.06, 4.48), chorioamnionitis (OR 4.61; 95% CI 2.89, 7.35), birth weight greater than 4000 g (OR 2.59; 95% CI 1.69, 3.97), maternal body mass index greater than 26 kg/m2 (OR 2.36; 95% CI 1.61, 3.47), Asian race (OR 2.35; 95% CI 1.04, 5.34), and magnesium sulfate use (OR 2.18; 95% CI 1.04, 4.55).
  
  
  CONCLUSIONS
  Elective induction of labor is associated with a significantly increased risk of cesarean delivery in nulliparous women. Avoiding labor induction in settings of unproved benefit may aid efforts to reduce the primary cesarean delivery rate.
authors.affiliation: Department of Obstetrics and Gynecology, Northwestern University Medical School, Northwestern Memorial Hospital, Chicago, Illinois, USA. stacyseyb@centura.org
authors.forename: S T
authors.initials: ST
authors.lastname: Seyb
authors.forename: R J
authors.initials: RJ
authors.lastname: Berka
authors.forename: M L
authors.initials: ML
authors.lastname: Socol
authors.forename: S L
authors.initials: SL
authors.lastname: Dooley
mesh_terms: D000293:Adolescent; D000328:Adult; D015992:Body Mass Index; D002585:Cesarean Section / Q000706:statistics & numerical data*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007751:Labor, Induced / Q000706:statistics & numerical data*; D010298:Parity; D011247:Pregnancy; D012307:Risk Factors