This is single centre pilot, randomized controlled trial assessing postpartum prophylactic anticoagulation with 3 weeks of LMWH followed by 3 weeks of Aspirin compared to standard of care of prophylactic LMWH for 6 weeks at moderate to high risk of developing VTE.

A single centre pilot, randomized controlled trial assessing postpartum prophylactic anticoagulation with 3 weeks of LMWH followed by 3 weeks of Aspirin compared to standard of care of prophylactic LMWH for 6 weeks for women at moderate to high risk of developing VTE to determine feasibility of conducting a large non inferiority trial using the same regimens.

Inclusion Criteria:

1. Personal history of unprovoked VTE prior to pregnancy or hormone associated VTE and not prescribed therapeutic anticoagulation or
2. Family history (1st degree relative) of VTE and antithrombin deficiency, protein C or protein S deficiency or
3. Combined thrombophilia or homozygous for the factor V Leiden mutation or prothrombin gene mutation, and family history of VTE (1st degree relative) and
4. > 18 years of age.

Exclusion Criteria:

1. Pre-existing indication for therapeutic LMWH

2. Contraindication to ASA:

   1. Known ASA allergy
   2. Documented history of gastrointestinal ulcer
   3. Known platelet count < 50x10^9/L at any time during the current pregnancy or postpartum

3. Contraindication to LMWH, e.g. known allergy

4. Active bleeding at any site, excluding physiological vaginal bleeding

5. Patients with bleeding disorders

6. Known severe hypertension (SBP >200mm/hg and/or DBP >120mm/hg) during the current pregnancy or postpartum