Question

36 weeks pregnant female on warfarin with mitral stenosis. What should we do?

• A. Shift to LMW Heparin
• B. Warfarin
• C. Switch to Aspirin
• D. Aspirin + Heparin

Hint:

Consider which anticoagulant does not cross the placenta and is therefore safe for the fetus near term.

Answer 1

The Correct Option is A

Step 1: Identify the clinical problem.
A 36-week pregnant woman with mitral stenosis is currently on warfarin. Warfarin is a vitamin K antagonist that crosses the placenta and is teratogenic (warfarin embryopathy in first trimester) and can cause fetal haemorrhage, especially near delivery.

Step 2: Understand anticoagulation in pregnancy near term.
At 36 weeks gestation (near term), the approach to anticoagulation changes critically:
- Warfarin crosses the placenta and can cause fetal intracranial haemorrhage during delivery (when fetal head is compressed through the birth canal).
- Low Molecular Weight Heparin (LMWH) does NOT cross the placenta (too large a molecule), making it safe for the fetus.
- LMWH is the preferred anticoagulant from 36 weeks until delivery in pregnant women requiring anticoagulation.

Step 3: Address the mitral stenosis context.
Heart valve disease (mitral stenosis) requires adequate anticoagulation to prevent thromboembolic events. LMWH provides effective anticoagulation without fetal risk, making it the ideal switch at 36 weeks.

Step 4: Exclude other options.
- Continue warfarin: fetal haemorrhage risk at delivery -- NOT appropriate at 36 weeks.
- Aspirin alone: inadequate anticoagulation for mitral stenosis with risk of thromboembolism.
- Aspirin + heparin: aspirin is antiplatelet, not anticoagulant; not standard regimen here.

Conclusion: Shift to Low Molecular Weight Heparin at 36 weeks.