Deep vein thrombosis: pregnancy: women with inherited thrombophilia may be at increased risk of VTE.

Clinical bottom line (level 4)

  1. Women with an inherited thrombophilia were at increased risk of venous thromboembolism during pregnancy (NNH = 10 at unknown) .
Friederich et al: Annals of Internal Medicine 1996; 125 (12): 955-960
Expires August 2003

The study

Case-control study with objective outcomes, not adjusted for confounding factors, not validated in an independent set of patients.

Setting: university outpatient clinics, Holland and Italy

129 patients (aged range 16 to 43 years; mean 26, 100% female) from families with documented antithrombin III, protein C or protein S deficiency, who had been pregnant
Cases: patients (% female, mean age ): venous thromboembolism during pregnancy
Controls: ?patients : no venous thromboembolism


Outcomes studied:
  • venous thromboembolism during pregnancy

    • Venous thromboembolism during pregnancy (documented by ultrasound, IPG, or venogram for DVT, or v/q scan or pulmonary angiogram for PE, or had clinical signs and had been treated for 3 months with anticoagulation).
    • 100% were followed until term.

    The evidence

    Patient expected event rate for venous thromboembolism during pregnancy: 1.5%
    risk factor venous thromboembolism during pregnancy
    present    		 venous thromboembolism during pregnancy
    absent    		 unadjusted OR
    (95% CI)    		 NNH
    (95% CI)
    thrombophilia 7 53 9.0
    (1.1 to 75)     		10
    (2 to 990)
    no thrombophilia 1 68

    Comments

    1. Many of the patients had no definitive test during pregnancy for VTE. Since clinical examination does not accurately predict VTE in patients, this makes OR less certain.
    2. If unblinded, clinical suspicion may have been increased markedly in those women with known inherited thrombophilias
    3. Do these results apply to women with a sporadic mutation?

    Citation

    1. Friederich PW, Sanson B-J, Simioni P, et al: frequency of pregnancy-related venous thromboembolism in anticoagulant factor-deficient women: implications for prophylaxis. Annals of Internal Medicine 1996; 125 (12): 955-960
    Contributor: Chris Ball and Clare Wotton, August 2000
    Reviewer: Paul Flynn

    Clinical Question.
    Patient pregnant women
    Intervention or Exposure inherited thrombophilia
    Outcome VTE