title: Assisted reproductive technology and severe postpartum haemorrhage: a case-control study.
abstract: OBJECTIVE
  To investigate the association between assisted reproductive technology and severe postpartum haemorrhage.
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  The study was conducted in Norway; Division of Gynaecology and Obstetrics at Oslo University Hospital and Department of Obstetrics and Gynaecology at Drammen Hospital.
  
  
  METHODS
  A source population including all women admitted for delivery at Oslo University Hospital and Drammen Hospital during the time period 1 January 2008 to 31 December 2011. The study population consisted of all cases of severe postpartum haemorrhage (n = 1064) and a random sample of controls (n = 2059).
  
  
  METHODS
  We used an explanatory strategy in the analysis, with multivariable logistic regression.
  
  
  METHODS
  Severe postpartum haemorrhage; defined as blood loss ≥1500 ml or need for blood transfusion.
  
  
  RESULTS
  Assisted reproductive technology was associated with an increased risk of severe postpartum haemorrhage (crude OR = 2.92; 95% CI 2.18-3.92, P < 0.001). Mode of delivery and anticoagulant medication had significant confounding effects. Strong interaction was found for multiple pregnancies. After adjusting for confounding and interaction, an increased risk was observed both in the strata of multiple pregnancies (adjusted OR = 7.00, 95% CI 2.70-18.12, P < 0.001), and in the strata of single gestation (adjusted OR = 1.58, 95% CI 1.12-2.24, P = 0.010).
  
  
  CONCLUSIONS
  Our findings warrant an increased awareness of the risk of severe postpartum haemorrhage in women conceiving with assisted reproductive technology. Furthermore, the high risk of severe postpartum haemorrhage in the presence of a twin or triplet pregnancy is an additional argument for single embryo transfer.
  
  
  CONCLUSIONS
  Assisted reproductive technology is associated with an increased risk of severe postpartum haemorrhage.
authors.affiliation: Division of Gynaecology and Obstetrics, Oslo University Hospital, Rikshospitalet, Oslo, Norway.|Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: L T
authors.initials: LT
authors.lastname: Nyfløt
authors.affiliation: Oslo Centre of Biostatistics and Epidemiology, Research Support Services, Oslo University Hospital, Oslo, Norway.
authors.forename: I
authors.initials: I
authors.lastname: Sandven
authors.affiliation: Section for Reproductive Medicine, Division of Gynaecology and Obstetrics, Oslo University Hospital, Oslo, Norway.
authors.forename: N B
authors.initials: NB
authors.lastname: Oldereid
authors.affiliation: Division of Gynaecology and Obstetrics, Oslo University Hospital, Rikshospitalet, Oslo, Norway.|Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: B
authors.initials: B
authors.lastname: Stray-Pedersen
authors.affiliation: Institute of Clinical Medicine, University of Oslo, Oslo, Norway.|Norwegian National Advisory Unit on Women's Health, Oslo University Hospital, Oslo, Norway.
authors.forename: S
authors.initials: S
authors.lastname: Vangen
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D016015:Logistic Models; D009664:Norway; D006473:Postpartum Hemorrhage / Q000209:etiology*; D011247:Pregnancy; D027724:Reproductive Techniques, Assisted / Q000009:adverse effects*; D012307:Risk Factors
keywords: Assisted reproductive technology; case-control; in vitro fertilisation; severe postpartum haemorrhage