Intervention: Lovenox
Trial phase: Phase 3
SMILES: CC(=O)NC1C(O)OC(COS(=O)(=O)O)C(OC2OC(C(=O)O)C(OC3OC(CO)C(OC4OC(C(=O)O)C(O)C(O)C4OS(=O)(=O)O)C(OS(=O)(=O)O)C3NS(=O)(=O)O)C(O)C2OS(=O)(=O)O)C1O
Sex: Female
Age groups: Adult | Older Adult
Healthy volunteers: No
Participants at risk: 30
Group description: Prophylactic-dose (5000 IU/0.2ml)low molecular weight heparin (LMWH), administered subcutaneously once daily in pre-filled glass syringes for 10 days (+/- 3 days) for a total of 10 (+/-3) study drug injections.

Dalteparin Sodium: 5,000 IU/0.2ml (anti-Xa) administered once daily in prefilled glass syringes.
Eligibility criteria:
Inclusion Criteria:

Women must be at high risk for thromboembolism for one of the following reasons:

Known low risk thrombophilia (Known = diagnosed prior to enrollment and low risk thrombophilia includes heterozygous factor V Leiden or prothrombin gene variant or protein C deficiency or protein S deficiency. If not previously tested then assumed not to have thrombophilia).
Immobilization (defined as >90% of waking hours in bed, of a week or more at any point in the antepartum period).

OR any two of the following reasons:

Postpartum infection (fever (temperature>38.5oC) and clinical signs/symptoms of infection and elevated neutrophil count (higher than local lab normal))
Postpartum hemorrhage (Estimated blood loss >1000 ml during delivery and postpartum)
Pre-pregnancy BMI >25 kg/m2
Emergency cesarean birth (emergency = not planned prior to onset of labour)
Smoking >5 cigarettes per day prior to pregnancy
Preeclampsia (blood pressure ≥ 140mmHG systolic and/or ≥90 mmHg diastolic on at least one occasion and proteinuria (1+ on urine dipstick or 300mg/dl or total excretion of 300mg/24 hours) or typical end-organ dysfunction.
Infant birth weight (adjusted for sex and gestational age) <3rd percentile (i.e., small for gestational age).

Exclusion Criteria:

Less than 6 hours or more than 36 hours since delivery at the time of randomization

Need for anticoagulation as judged by the local investigator, may include but not limited to:

Personal history of previous provoked or unprovoked VTE (DVT or PE)
Continuation of LMWH that was started in the antenatal period for VTE prophylaxis
Mechanical heart valve
Known high-risk thrombophilia (Known = diagnosed prior to enrolment and high-risk thrombophilia includes deficiency of antithrombin (at least 1 abnormal lab result), persistently positive anticardiolipin antibodies (> 30U/ml on two measurements a minimum of six weeks apart), persistently positive Anti B2 glycoprotein antibodies (> 20U/ml on two measurements a minimum of six weeks apart), persistently positive lupus anticoagulant (positive on two measurements a minimum of six weeks apart), homozygous factor V Leiden (FVL), homozygous prothrombin gene mutation (PGM), compound heterozygosity factor V Leiden (FVL) and prothrombin gene mutations (PGM), more than 1 thrombophilia (any combination of 2 or more: FVL, PGM, protein C deficiency, protein S deficiency). If not previously tested then assumed not to have thrombophilia).

Contraindication to heparin therapy, including:

History of heparin induced thrombocytopenia (HIT)
Platelet count of less than 80,000 x 106/L on postpartum Complete Blood Count(CBC)
Hemoglobin ≤ 75 g/L on postpartum CBC
Active bleeding at any site (not resolved prior to randomization)
Excessive postpartum vaginal bleeding (>1 pad per hour prior to randomization).
Documented gastrointestinal ulcer within 6 weeks prior to randomization
History of heparin or LMWH allergy
Severe postpartum hypertension (systolic blood pressure (SBP) > 200mm/hg and/or diastolic blood pressure (DBP) > 120mm/hg)
Severe hepatic failure (INR >1.8 if liver disease suspected)
Have received more than one dose of heparin or LMWH since delivery
< age of legal majority in local jurisdiction (age <18 in Canada)
Prior participation in PROSPER
Unable or refused to consent