title: Postpartum hemorrhage following vaginal delivery: risk factors and maternal outcomes.
abstract: Limited understanding of risk factors exists for postpartum hemorrhage (PPH) post-vaginal delivery. The aim of this study was to identify risk factors for PPH post-vaginal delivery within a contemporary obstetric cohort.
  
  
  
  Retrospective case-control study. PPH was classified by an estimated blood loss ⩾500 ml. Risk factors for PPH were identified using univariable and multivariable logistic regression. We secondarily investigated maternal outcomes and medical and surgical interventions for PPH management.
  
  
  
  The study cohort comprised 159 cases and 318 controls. Compared with a second-stage duration <2 h, a second stage⩾3 h was associated with PPH (adjusted odds ratio=2.3; 95% CI=1.2 to 4.6). No other clinical or obstetric variables were identified as independent risk factors for PPH. Among cases, 4% received red blood cells and 1% required intensive care admission.
  
  
  
  Although PPH-related morbidity may be uncommon after vaginal delivery, PPH should be anticipated for women after a second stage ⩾3 h.
authors.affiliation: Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Miller
authors.affiliation: Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: S
authors.initials: S
authors.lastname: Cohn
authors.affiliation: Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: S
authors.initials: S
authors.lastname: Akdagli
authors.affiliation: Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: B
authors.initials: B
authors.lastname: Carvalho
authors.affiliation: Department of Obstetrics and Gynecology, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: Y J
authors.initials: YJ
authors.lastname: Blumenfeld
authors.affiliation: Department of Anesthesiology, Perioperative, and Pain Medicine, Stanford University School of Medicine, Stanford, CA, USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Butwick
mesh_terms: D000328:Adult; D002140:California; D016022:Case-Control Studies; D036861:Delivery, Obstetric / Q000009:adverse effects* / Q000379:methods; D005260:Female; D006801:Humans; D016015:Logistic Models; D015999:Multivariate Analysis; D016017:Odds Ratio; D006473:Postpartum Hemorrhage / Q000453:epidemiology* / Q000628:therapy; D011247:Pregnancy; D012189:Retrospective Studies; D012307:Risk Factors; D062606:Tertiary Care Centers