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Table 1 Potential precipitating risk factors assessed regarding the past venous thromboembolic event Minor transient (i.e. now resolved) risk factors within 8 weeks of initial VTE

From: Evaluating patient values and preferences for thromboprophylaxis decision making during pregnancy: a study protocol

Minor transient (i.e. now resolved) risk factors within 8 weeks of initial VTE Major transient (i.e. now resolved) risk factors within 8 weeks of initial VTE Known hypercoagulable state
Pregnancy Leg casting Deficiency of antithrombin, protein C, or protein S
Postpartum (defined as 6 weeks after delivery) Major surgery (>30 minutes; general or spinal anesthesia) Activated protein C resistance/factor V Leiden
Hormonal contraception (birth control pill, patch or needle) Acute medical illness with hospital admission for ≥ 3 days Prothrombin gene mutation
Airplane travel (longer than 6 hours) Immobilization ≥ 3 days (in bed except to go to washroom) Anticardiolipin antibody positivity
  Active cancer Nonspecific inhibitor