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Heparin and Warfarin in Pregnancy
Dr. S.0 MIKAYE/LinkedIn
Dec 11, 2025, 23:03

Heparin and Warfarin in Pregnancy

Samwel Mikaye, CEO of SaMik Medical Center, posted on LinkedIn:

”HEPARIN AND WARFARIN IN PREGNANCY

Anticoagulation may be necessary in pregnancy for conditions like mechanical heart valves, thrombophilia, or previous thromboembolism.

Key principle: Choose an anticoagulant that protects the mother without harming the fetus.

1. HEPARIN

Types
• Unfractionated heparin (UFH)
• Low molecular weight heparin (LMWH) – e.g., Enoxaparin, Dalteparin

Safety
• Does NOT cross the placenta → safe for the fetus
• Preferred anticoagulant in pregnancy, especially in the first trimester

Administration
• UFH: Subcutaneous or IV, frequent monitoring (aPTT)
• LMWH: Subcutaneous, fixed or weight-based dosing, less monitoring needed

Adverse Effects
• Maternal bleeding
• Heparin-induced thrombocytopenia (HIT) – rare with LMWH
• Osteoporosis (with prolonged UFH use)

2. WARFARIN

Safety
• Crosses the placenta → teratogenic
• Avoid in the first trimester due to risk of warfarin embryopathy (nasal hypoplasia, limb defects)
• Risk of fetal bleeding and CNS abnormalities in later trimesters

When Warfarin May Be Used
• In selected high-risk women with mechanical heart valves, after the first trimester, if benefits outweigh risks
• Usually switched to heparin during weeks 6–12, then back to warfarin until near delivery

Monitoring
• Maternal INR target: 2.0–3.0 (varies with valve type)
• Close fetal monitoring recommended

3. MANAGEMENT PRINCIPLES
• First trimester: Prefer LMWH or UFH
• Second trimester: Warfarin may be considered if necessary
• Near term: Switch back to heparin to reduce the risk of fetal bleeding at delivery
• Always coordinate with obstetrics and hematology

KEY POINTS
• Heparin (UFH or LMWH) is safe in all trimesters; does not cross placenta
• Warfarin is teratogenic, especially in the first trimester, and causes fetal bleeding
• Careful switching strategy is required for women with mechanical heart valves
• Close maternal and fetal monitoring is essential”

Pregnancy

Stay updated with Hemostasis Today.

Anticoagulation deep vein thrombosis DVT Health Hematology Hemostasis Hemostasis Today Heparin LMWH Medicine Pregnancy Samik Medical Center Samwel Mikaye Thrombophilia thrombosis UFH venous thromboembolism Vitamin K antagonists VTE Warfarin
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