Inclusion Criteria:  Personal history of unprovoked VTE prior to pregnancy or hormone associated VTE and not prescribed therapeutic anticoagulation or Family history (1st degree relative) of VTE and antithrombin deficiency, protein C or protein S deficiency or Combined thrombophilia or homozygous for the factor V Leiden mutation or prothrombin gene mutation, and family history of VTE (1st degree relative) and > 18 years of age.  Exclusion Criteria:  Pre-existing indication for therapeutic LMWH  Contraindication to ASA:  Known ASA allergy Documented history of gastrointestinal ulcer Known platelet count < 50x10^9/L at any time during the current pregnancy or postpartum Contraindication to LMWH, e.g. known allergy Active bleeding at any site, excluding physiological vaginal bleeding Patients with bleeding disorders Known severe hypertension (SBP >200mm/hg and/or DBP >120mm/hg) during the current pregnancy or postpartum