title: Safety of withholding heparin in pregnant women with a history of venous thromboembolism. Recurrence of Clot in This Pregnancy Study Group.
abstract: BACKGROUND
  Women with a history of venous thromboembolism may be at increased risk for venous thromboembolic events during pregnancy. In these women, the decision to give or withhold heparin in the antepartum period is controversial, because accurate estimates of the frequency of recurrent thromboembolic events if antepartum heparin is withheld are not available.
  
  
  METHODS
  We prospectively studied 125 pregnant women with a single previous episode of venous thromboembolism. Antepartum heparin was withheld, but anticoagulant therapy was given for four to six weeks post partum. Our primary objective was to determine the rate of antepartum recurrence of venous thromboembolism. Laboratory studies were performed to identify thrombophilia in 95 women.
  
  
  RESULTS
  Three of the 125 women (2.4 percent) had an antepartum recurrence of venous thromboembolism (95 percent confidence interval, 0.2 to 6.9 percent). There were no recurrences in the 44 women who had no evidence of thrombophilia and who also had a previous episode of thrombosis that was associated with a temporary risk factor. Among the 51 women with abnormal laboratory results or a previous episode of idiopathic thrombosis, or both, 3 (5.9 percent) had an antepartum recurrence of venous thromboembolism (95 percent confidence interval, 1.2 to 16.2 percent).
  
  
  CONCLUSIONS
  The risk of recurrent antepartum venous thromboembolism in women with a history of venous thromboembolism is low, and therefore routine antepartum prophylaxis with heparin is not warranted.
authors.affiliation: McMaster University Medical Centre, Hamilton, Ont, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Brill-Edwards
authors.forename: J S
authors.initials: JS
authors.lastname: Ginsberg
authors.forename: M
authors.initials: M
authors.lastname: Gent
authors.forename: J
authors.initials: J
authors.lastname: Hirsh
authors.forename: R
authors.initials: R
authors.lastname: Burrows
authors.forename: C
authors.initials: C
authors.lastname: Kearon
authors.forename: W
authors.initials: W
authors.lastname: Geerts
authors.forename: M
authors.initials: M
authors.lastname: Kovacs
authors.forename: J I
authors.initials: JI
authors.lastname: Weitz
authors.forename: K S
authors.initials: KS
authors.lastname: Robinson
authors.forename: R
authors.initials: R
authors.lastname: Whittom
authors.forename: G
authors.initials: G
authors.lastname: Couture
mesh_terms: D000328:Adult; D000925:Anticoagulants / Q000627:therapeutic use*; D001798:Blood Proteins / Q000032:analysis; D005260:Female; D006493:Heparin / Q000627:therapeutic use*; D006801:Humans; D015994:Incidence; D011247:Pregnancy / Q000097:blood; D011249:Pregnancy Complications, Cardiovascular / Q000453:epidemiology / Q000517:prevention & control*; D011295:Prenatal Care; D011446:Prospective Studies; D011655:Pulmonary Embolism / Q000517:prevention & control; D012307:Risk Factors; D055502:Secondary Prevention; D013923:Thromboembolism / Q000453:epidemiology / Q000517:prevention & control*; D020246:Venous Thrombosis / Q000517:prevention & control
chemical_list: D000925:Anticoagulants; D001798:Blood Proteins; D006493:Heparin