PROSPER: PostpaRtum PrOphylaxiS for PE Randomized Control Trial Pilot

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

1. Known low risk thrombophilia (Known = diagnosed prior to enrollment and low riskthrombophilia includes heterozygous factor V Leiden or prothrombin gene variant orprotein C deficiency or protein S deficiency. If not previously tested then assumednot to have thrombophilia).

2. Immobilization (defined as >90% of waking hours in bed, of a week or more at any pointin the antepartum period). OR any two of the following reasons:

3. Postpartum infection (fever (temperature>38.5oC) and clinical signs/symptoms ofinfection and elevated neutrophil count (higher than local lab normal))

4. Postpartum hemorrhage (Estimated blood loss >1000 ml during delivery and postpartum)

5. Pre-pregnancy BMI >25 kg/m2

6. Emergency cesarean birth (emergency = not planned prior to onset of labour)

7. Smoking >5 cigarettes per day prior to pregnancy

8. Preeclampsia (blood pressure ≥ 140mmHG systolic and/or ≥90 mmHg diastolic on at leastone occasion and proteinuria (1+ on urine dipstick or 300mg/dl or total excretion of 300mg/24 hours) or typical end-organ dysfunction.

9. Infant birth weight (adjusted for sex and gestational age) <3rd percentile (i.e.,small for gestational age).

Exclusion Criteria:

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

2. Need for anticoagulation as judged by the local investigator, may include but notlimited to:

3. Personal history of previous provoked or unprovoked VTE (DVT or PE)

4. Continuation of LMWH that was started in the antenatal period for VTE prophylaxis

5. Mechanical heart valve

6. Known high-risk thrombophilia (Known = diagnosed prior to enrolment and high-riskthrombophilia includes deficiency of antithrombin (at least 1 abnormal labresult), persistently positive anticardiolipin antibodies (> 30U/ml on twomeasurements a minimum of six weeks apart), persistently positive Anti B2glycoprotein antibodies (> 20U/ml on two measurements a minimum of six weeksapart), persistently positive lupus anticoagulant (positive on two measurements aminimum of six weeks apart), homozygous factor V Leiden (FVL), homozygousprothrombin gene mutation (PGM), compound heterozygosity factor V Leiden (FVL)and prothrombin gene mutations (PGM), more than 1 thrombophilia (any combinationof 2 or more: FVL, PGM, protein C deficiency, protein S deficiency). If notpreviously tested then assumed not to have thrombophilia).

7. Contraindication to heparin therapy, including:

8. History of heparin induced thrombocytopenia (HIT)

9. Platelet count of less than 80,000 x 106/L on postpartum Complete BloodCount(CBC)

10. Hemoglobin ≤ 75 g/L on postpartum CBC

11. Active bleeding at any site (not resolved prior to randomization)

12. Excessive postpartum vaginal bleeding (>1 pad per hour prior to randomization).

13. Documented gastrointestinal ulcer within 6 weeks prior to randomization

14. History of heparin or LMWH allergy

15. Severe postpartum hypertension (systolic blood pressure (SBP) > 200mm/hg and/ordiastolic blood pressure (DBP) > 120mm/hg)

16. Severe hepatic failure (INR >1.8 if liver disease suspected)

17. Have received more than one dose of heparin or LMWH since delivery

18. < age of legal majority in local jurisdiction (age <18 in Canada)

19. Prior participation in PROSPER

20. Unable or refused to consent