title: Effects of onset of labor and mode of delivery on severe postpartum hemorrhage.
abstract: OBJECTIVE
  Our purpose was to study the impact of labor onset and delivery mode on the risk of severe postpartum hemorrhage.
  
  
  METHODS
  This was a population-based study of 307,415 mothers who were registered in the Medical Birth Registry of Norway from 1999-2004.
  
  
  RESULTS
  Severe postpartum hemorrhage occurred in 1.1% of all mothers and in 2.1% of those mothers with previous cesarean section delivery (CS). Compared with spontaneous labor, hemorrhage risk was higher for induction (odds ratio [OR], 1.71; 95% confidence interval [CI], 1.56-1.88) and prelabor CS (OR, 2.05; 95% CI, 1.84-2.29). The risk was 55% higher for emergency CS and half that for vaginal deliveries (OR, 0.48; 95% CI, 0.43-0.53), compared with prelabor CS. The highest risk was for emergency CS after induction in mothers with previous CS (OR, 6.57; 95% CI, 4.25-10.13), compared with spontaneous vaginal delivery in mothers with no previous CS.
  
  
  CONCLUSIONS
  Induction and prelabor CS should be practiced with caution because of the increased risk of severe postpartum hemorrhage.
authors.affiliation: Division of Obstetrics and Gynecology, Faculty of Medicine, University of Oslo, Rikshospitalet, Oslo, Norway. iqbal.al-zirqi@rikshospitalet.no
authors.forename: Iqbal
authors.initials: I
authors.lastname: Al-Zirqi
authors.forename: Siri
authors.initials: S
authors.lastname: Vangen
authors.forename: Lisa
authors.initials: L
authors.lastname: Forsén
authors.forename: Babill
authors.initials: B
authors.lastname: Stray-Pedersen
mesh_terms: D002585:Cesarean Section / Q000009:adverse effects; D017604:Cesarean Section, Repeat; D004632:Emergency Medical Services; D005260:Female; D006801:Humans; D007745:Labor Onset; D016015:Logistic Models; D006473:Postpartum Hemorrhage / Q000453:epidemiology*; D011247:Pregnancy; D014219:Trial of Labor