title: Maternal complications of pregnancy increase beyond 40 weeks of gestation in low-risk women.
abstract: OBJECTIVE
  We sought to determine when rates of maternal pregnancy complications increase for low-risk nulliparous and multiparous women at term.
  
  
  METHODS
  We designed a retrospective cohort study of low-risk women delivered beyond 37 weeks gestational age from 1976 to 2001. Rates of mode of delivery and maternal complications of labor and delivery were examined by gestational age with both bivariate and multivariate analyses. Statistical significance was designated by P<0.05.
  
  
  RESULTS
  We found that among the 32,828 low-risk women who delivered at 37 completed weeks and beyond, the rates of primary cesarean delivery, operative vaginal delivery, third- or fourth-degree perineal lacerations, and chorioamnionitis all increased at 40 weeks of gestation (P<0.001), and the rate of postpartum hemorrhage increased at 41 weeks of gestation (P<0.001). These increases of rates of complications were larger and increased at an earlier gestational age among nulliparous women.
  
  
  CONCLUSIONS
  We found that the risk of maternal complications for otherwise low risk nulliparous and multiparous women increased as pregnancy progressed beyond 40 weeks of gestation. Counseling of women who progress past their EDC should include comparing the risks of induction of labor to that of expectant management.
authors.affiliation: Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco, 94143, USA. abcmd@berkeley.edu
authors.forename: A B
authors.initials: AB
authors.lastname: Caughey
authors.forename: J T
authors.initials: JT
authors.lastname: Bishop
mesh_terms: D000328:Adult; D002140:California / Q000453:epidemiology; D015331:Cohort Studies; D036861:Delivery, Obstetric / Q000706:statistics & numerical data; D005260:Female; D005865:Gestational Age; D006801:Humans; D007744:Obstetric Labor Complications / Q000453:epidemiology* / Q000209:etiology; D006473:Postpartum Hemorrhage; D011247:Pregnancy; D011256:Pregnancy Outcome; D011273:Pregnancy, Prolonged; D012189:Retrospective Studies