Mechanical valve in early pregnancy — preconception and anticoagulation counselling station

You are the obstetric registrar in a tertiary centre. A 32-year-old G1P0 at 8 weeks gestation with a mechanical mitral valve (St Jude Medical, inserted six years ago for severe rheumatic mitral regurgitation) presents for her booking visit. She is on long-term warfarin 5 mg daily. She has read online that warfarin causes birth defects and asks whether she should stop it. Her blood pressure is 118/72 mmHg, sinus rhythm, normal LV function, well-functioning mechanical valve on recent echocardiogram. Her partner is present. The assessor runs the clock and feeds you the woman's questions and her emotional responses.