The goal of this clinical trial is to evaluate the risk-benefit of a short-term treatment with a low-dose low-molecular-weight heparin (LMWH), in the postpartum period (after delivery). The main questions it aims to answer are:

• compared to no treatment, does short-term postpartum LMWH modify the risk of venous thromboembolism within 90 days of delivery?
• compared to no treatment, does short-term postpartum LMWH modify the risks of bleeding and wound complications? Participants will take low-dose LMWH for 7-10 days or no treatment, and will be followed for 90 days post-delivery.

Inclusion Criteria: postpartum women after delivery AND ≥1 major risk factor / ≥2 minor risk factors:

• Major risk factors: Emergency cesarean section ; Pre-pregnancy BMI ≥35kg/m2 ; Known low-risk thrombophilia (heterozygous factor V Leiden; heterozygous G20210 prothrombin mutation) ; Pre-eclampsia ; Pre-term delivery ; Peripartum systemic infection ; Intra-uterine growth restriction ; Pregnancy loss
• Minor risk factors: Age ≥35 years ; Pre-pregnancy BMI 30.0-34.9kg/m2 ; Current smoking ; Elective cesarean section ; Postpartum hemorrhage ; Antenatal immobility

Exclusion Criteria:

• ≥2 doses of postpartum LMWH
• Any indication for therapeutic anticoagulation
• A high-risk of postpartum VTE
• An increased bleeding risk
• A contra-indication to heparin