title: Atonic Postpartum Hemorrhage: Blood Loss, Risk Factors, and Third Stage Management.
abstract: Atonic postpartum hemorrhage rates have increased in many industrialized countries in recent years. We examined the blood loss, risk factors, and management of the third stage of labour associated with atonic postpartum hemorrhage.
  
  
  
  We carried out a case-control study of patients in eight tertiary care hospitals in Canada between January 2011 and December 2013. Cases were defined as women with a diagnosis of atonic postpartum hemorrhage, and controls (without postpartum hemorrhage) were matched with cases by hospital and date of delivery. Estimated blood loss, risk factors, and management of the third stage labour were compared between cases and controls. Conditional logistic regression was used to adjust for confounding.
  
  
  
  The study included 383 cases and 383 controls. Cases had significantly higher mean estimated blood loss than controls. However, 16.7% of cases who delivered vaginally and 34.1% of cases who delivered by Caesarean section (CS) had a blood loss of < 500 mL and < 1000 mL, respectively; 8.2% of controls who delivered vaginally and 6.7% of controls who delivered by CS had blood loss consistent with a diagnosis of postpartum hemorrhage. Factors associated with atonic postpartum hemorrhage included known protective factors (e.g., delivery by CS) and risk factors (e.g., nulliparity, vaginal birth after CS). Uterotonic use was more common in cases than in controls (97.6% vs. 92.9%, P < 0.001). Delayed cord clamping was only used among those who delivered vaginally (7.7% cases vs. 14.6% controls, P = 0.06).
  
  
  
  There is substantial misclassification in the diagnosis of atonic postpartum hemorrhage, and this could potentially explain the observed temporal increase in postpartum hemorrhage rates.
authors.affiliation: Department of Obstetrics and Gynaecology, University of British Columbia and the Children's and Women's Hospital and Health Centre of British Columbia, Vancouver BC; School of Population and Public Health, University of British Columbia, Vancouver BC.
authors.forename: Sarka
authors.initials: S
authors.lastname: Lisonkova
authors.affiliation: Department of Obstetrics and Gynaecology, University of British Columbia and the Children's and Women's Hospital and Health Centre of British Columbia, Vancouver BC.
authors.forename: Azar
authors.initials: A
authors.lastname: Mehrabadi
authors.affiliation: Department of Obstetrics and Gynaecology, Dalhousie University, Halifax NS.
authors.forename: Victoria M
authors.initials: VM
authors.lastname: Allen
authors.affiliation: Centre de recherché en biologie de la reproduction et Centre de recherché du CHU de Québec, Université Laval, Québec QC.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Bujold
authors.affiliation: Department of Obstetrics and Gynecology, Memorial University, St. John's NL.
authors.forename: Joan M G
authors.initials: JM
authors.lastname: Crane
authors.affiliation: Department of Obstetrics and Gynecology, University of Ottawa, Ottawa ON.
authors.forename: Laura
authors.initials: L
authors.lastname: Gaudet
authors.affiliation: London Health Sciences Centre, Department of Obstetrics and Gynaecology, London Western University, London ON.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Gratton
authors.affiliation: Sunnybrook Health Sciences Centre, Toronto ON.
authors.forename: Noor Niyar N
authors.initials: NN
authors.lastname: Ladhani
authors.affiliation: Department of Obstetrics and Gynecology and Reproductive Sciences, University of Saskatchewan, Saskatoon SK.
authors.forename: Olufemi A
authors.initials: OA
authors.lastname: Olatunbosun
authors.affiliation: Department of Obstetrics and Gynaecology, University of British Columbia and the Children's and Women's Hospital and Health Centre of British Columbia, Vancouver BC; School of Population and Public Health, University of British Columbia, Vancouver BC.
authors.forename: K S
authors.initials: KS
authors.lastname: Joseph
mesh_terms: D000328:Adult; D002170:Canada / Q000453:epidemiology; D016022:Case-Control Studies; D036861:Delivery, Obstetric; D005260:Female; D006801:Humans; D007749:Labor Stage, Third; D008297:Male; D006473:Postpartum Hemorrhage / Q000453:epidemiology* / Q000628:therapy*; D011247:Pregnancy; D011248:Pregnancy Complications; D012307:Risk Factors; D055815:Young Adult
keywords: Postpartum hemorrhage; blood loss; risk factors; third stage