title: Interbirth interval with frequency of cesarean delivery.
abstract: OBJECTIVE
  To estimate whether and to what extent interbirth interval is associated with cesarean delivery.
  
  
  METHODS
  This is a retrospective cohort study of 2,528 multiparous women who presented to labor and delivery at a single tertiary care obstetric hospital during an 18-month period. Women were grouped by their interdelivery interval in 5-year increments, and the rate of cesarean delivery was determined for these groups. The independent association of interdelivery interval with cesarean delivery was further estimated after controlling for potential confounding factors in logistic regression.
  
  
  RESULTS
  Women with an interbirth interval of less than 5 years had a cesarean delivery rate of 1.9%. Women with interbirth intervals of 5-9 years, 10-14 years, and 15 or more years had cesarean delivery rates of 5.0%, 7.7%, and 13.3%, respectively (P<.001). After controlling for potential confounding factors, the corresponding odds ratio (and 95% confidence intervals) for cesarean delivery for each respective interdelivery interval group, in reference to the "less than 5 years" group, was 2.1 (1.12-3.92), 3.2 (1.17-8.63), and 7.2 (1.47-35.53).
  
  
  CONCLUSIONS
  A longer interbirth interval is independently associated with an increased risk of cesarean delivery.
authors.affiliation: From the Department of Obstetrics and Gynecology, Northwestern University Medical School, Chicago, Illinois.
authors.forename: Emily S
authors.initials: ES
authors.lastname: Miller
authors.forename: William A
authors.initials: WA
authors.lastname: Grobman
mesh_terms: D000328:Adult; D001721:Birth Intervals / Q000706:statistics & numerical data*; D002585:Cesarean Section / Q000706:statistics & numerical data*; D015986:Confounding Factors, Epidemiologic; D005260:Female; D006801:Humans; D016015:Logistic Models; D011247:Pregnancy; D012189:Retrospective Studies; D018570:Risk Assessment