The Modified WHO (mWHO) classification of cardiovascular disease in pregnancy categorises conditions by maternal mortality/morbidity risk. A woman with a mechanical prosthetic heart valve falls into which category, and what is the recommended anticoagulation in the first trimester?

• A mWHO III; low molecular weight heparin throughout pregnancy
• B mWHO III–IV; warfarin throughout (or LMWH if dose-adjusted) with higher valve thrombosis risk on LMWH ✓
• C mWHO IV; pregnancy contraindicated; if pregnant, warfarin until 36 weeks
• D mWHO II; unfractionated heparin throughout pregnancy is standard

Explanation

Mechanical prosthetic heart valves are classified mWHO III (if well-functioning with no other complications) and require anticoagulation throughout pregnancy. Warfarin is the most effective anticoagulant for mechanical valves and carries the lowest valve thrombosis risk, but is a teratogen (warfarin embryopathy) especially when used at doses requiring >5 mg/day during 6–12 weeks gestation. LMWH (dose-adjusted, anti-Xa monitored) is an alternative in the first trimester if the warfarin dose is ≤5 mg/day, but carries higher valve thrombosis rates. The decision must be individualised based on valve type, position, and warfarin dose.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.