title: The risk of postpartum hemorrhage in women using high dose of low-molecular-weight heparins during pregnancy.
abstract: BACKGROUND
  Low-molecular-weight heparins (LMWH) are the most commonly used anticoagulant during pregnancy for prevention or treatment of VTE. However, the size of the associated risk of postpartum haemorrhage (PPH) is unknown.
  
  
  OBJECTIVE
  To assess the bleeding risk of high dose LMWH, also in relation to time between last dose LMWH and delivery.
  
  
  METHODS
  From 1999 to 2009, we followed 88 pregnant women who were started on therapeutic anticoagulation. Controls were pregnant women without LMWH, matched 1:4 for parity, mode of delivery, age, gestational age and delivery date. PPH was defined as >500 ml blood loss for vaginal delivery (severe PPH in vaginal delivery as >1000 ml) and >1000 ml for cesarean section (CS). Women were divided into subgroups by the interval between last dose of anticoagulation and delivery (<12, 12-24 hrs, >24 hrs).
  
  
  RESULTS
  Risk of PPH after vaginal delivery was 30% and 18% for LMWH-users and non-users, respectively (OR 1.9, 95%CI 1.1-3.5). Risk of severe PPH after vaginal delivery was not different (5.6 vs 5.0%; OR 1.1; 0.4-3.6). Risk of PPH after CS was 12% in LMWH-users and 4% in non-users (OR 2.9; 0.5-19.4). Both events of LMWH-users occurred after emergency CS. The risk of PPH associated with delivery within 24 hours after last dose of LMWH was 1.2 fold higher (95%CI 0.4-3.6) compared to a larger interval.
  
  
  CONCLUSIONS
  High dose LMWH carries an increased risk of more than 500 mL blood loss after vaginal delivery. However, this results not in more clinical relevant severe PPHs. The interval between last dose of LMWH and delivery does not influence the risk of PPH.
authors.affiliation: Division of Haemostasis and Thrombosis, Department of Haematology, University Medical Centre Groningen, The Netherlands. h.m.knol@og.umcg.nl
authors.forename: H Marieke
authors.initials: HM
authors.lastname: Knol
authors.forename: Lejan
authors.initials: L
authors.lastname: Schultinge
authors.forename: Nic J G M
authors.initials: NJ
authors.lastname: Veeger
authors.forename: Hanneke C
authors.initials: HC
authors.lastname: Kluin-Nelemans
authors.forename: Jan J H M
authors.initials: JJ
authors.lastname: Erwich
authors.forename: Karina
authors.initials: K
authors.lastname: Meijer
mesh_terms: D000328:Adult; D015897:Comorbidity; D064420:Drug-Related Side Effects and Adverse Reactions / Q000453:epidemiology*; D005260:Female; D006495:Heparin, Low-Molecular-Weight / Q000008:administration & dosage*; D006801:Humans; D015994:Incidence; D009426:Netherlands / Q000453:epidemiology; D006473:Postpartum Hemorrhage / Q000453:epidemiology*; D011247:Pregnancy; D011249:Pregnancy Complications, Cardiovascular / Q000453:epidemiology* / Q000517:prevention & control*; D012189:Retrospective Studies; D012307:Risk Factors; D054556:Venous Thromboembolism / Q000453:epidemiology* / Q000517:prevention & control*; D014930:Women
chemical_list: D006495:Heparin, Low-Molecular-Weight