Drug of Choice for DVT and PE in Pregnancy
Low-molecular-weight heparin (LMWH) is the drug of choice for treating deep vein thrombosis and pulmonary embolism in pregnancy, strongly preferred over unfractionated heparin, while warfarin and factor Xa inhibitors are contraindicated. 1
Primary Recommendation
The American Society of Hematology (2018) provides a strong recommendation for LMWH over unfractionated heparin (UFH) for pregnant women with acute VTE, based on moderate certainty evidence. 1 This recommendation is echoed by the European Society of Cardiology, which explicitly states that "LMWH has become the drug of choice for the treatment of VTE in pregnancy and puerperium." 1
Why LMWH is Superior
LMWH offers multiple advantages over UFH in pregnancy:
- Lower bleeding risk: Major bleeding occurs in only 1.41% of patients during the antepartum period and 1.90% in the first 24 hours after delivery 2
- Reduced heparin-induced thrombocytopenia: Markedly lower incidence (0% vs 2.7% in non-pregnant populations) compared to UFH 1
- Minimal osteoporosis risk: Only 0.04% incidence with LMWH versus 2.2% with extended UFH use 1
- Better efficacy: Recurrent VTE rate of only 1.15-1.97% during pregnancy with LMWH treatment 1, 2
- Superior bioavailability and convenience: Once or twice daily dosing without routine monitoring required 1, 3
Contraindicated Options
Warfarin is absolutely contraindicated throughout pregnancy due to:
- Teratogenicity, particularly in the first trimester causing embryopathy 1, 3
- Risk of fetal bleeding and neurodevelopmental deficits 1
- Crosses the placenta freely 4
Factor Xa inhibitors (rivaroxaban, apixaban, edoxaban) and all direct oral anticoagulants are absolutely contraindicated in pregnancy because they cross the placental barrier and their reproductive effects in humans are unknown. 1, 3
Dosing and Monitoring
- Weight-based therapeutic dosing: Enoxaparin 1 mg/kg twice daily or dalteparin 100 IU/kg twice daily 1
- Routine anti-Xa monitoring is not recommended for most pregnant women receiving therapeutic LMWH 1
- Continue treatment for at least 6 weeks postpartum with minimum total duration of 3 months from diagnosis 3, 5
When UFH May Be Considered
UFH remains an option only in specific circumstances:
- Severe renal impairment (creatinine clearance <30 mL/min), as LMWH accumulates renally 1, 3
- Heparin-induced thrombocytopenia history, where danaparoid or fondaparinux (with caution) should be used instead 1
Peripartum Management
- Discontinue LMWH at least 24 hours before planned delivery or neuraxial anesthesia 3, 6, 5
- Resume anticoagulation postpartum and continue for at least 6 weeks 3
- LMWH, UFH, and warfarin are all safe during breastfeeding 1, 3
Common Pitfalls to Avoid
- Do not use oral anticoagulants during pregnancy, even if the patient was previously stable on them 1, 3
- Do not assume prophylactic doses are adequate for acute VTE treatment—therapeutic weight-based dosing is required 1
- Do not delay treatment while awaiting diagnostic confirmation if clinical suspicion is high 1
Answer: d. Low-molecular-weight heparin (LMWH)