Need for Antepartum Thromboprophylaxis in Pregnant Women With One Prior Episode of Venous Thromboembolism (VTE)

Prospective Study Assessing the Need for Antepartum Thromboprophylaxis in Pregnant Women With One Prior Episode of Venous Thromboembolism

Pregnant women with a prior history of venous thromboembolism (VTE) are at increased risk of recurrent VTE. Current guidelines assessing the role of prophylaxis in pregnant women with prior VTE are based primarily on expert opinion and the optimal clinical management strategy remains unclear.

This multicentre, prospective cohort study aims to test the following hypotheses:

1. Antepartum prophylaxis with fixed-dose low molecular-weight heparin (LMWH) is safe, convenient and associated with an acceptably low risk of recurrent VTE in women with a single prior episode of VTE that was either unprovoked or associated with a minor transient risk factor. (Moderate risk cohort)
2. Withholding antepartum prophylaxis is safe (recurrence risk <1%) in pregnant women with a single prior episode of VTE provoked by a major transient risk factor. (Low risk cohort)

All study patients will receive 6 weeks of postpartum prophylaxis.

Inclusion Criteria:

• Confirmed pregnancy (positive serum or urine)
• At least 18 years of age
• History of one prior episode of VTE consisting of DVT (diagnosed by compression ultrasonography [CUS] or venography) and/or PE (diagnosed by ventilation-perfusion [V/Q] lung scintigraphy, computed tomographic pulmonary angiography [CTPA], or traditional pulmonary angiography)

Exclusion Criteria:

• Ongoing need for therapeutic anticoagulation for prevention or treatment of cardioembolic stroke
• Known high-risk thrombophilia (specifically antithrombin deficiency, protein S deficiency, protein C deficiency, homozygosity for the factor V Leiden or prothrombin G20210A mutations, antiphospholipid antibody or compound abnormalities)
• VTE within 3 months of the current pregnancy
• Clinical risk factor for initial episode of VTE, if present, not resolved (excluding pregnancy)
• Known contraindication to anticoagulation (including active, uncontrolled bleeding or major bleed within the previous 4 weeks)
• For patients with prior unprovoked VTE, contraindication to LMWH (including allergy, HIT, impaired renal function, osteoporosis)
• Geographic or social factors precluding follow-up
• Inability or unwillingness to provide informed consent