COUMARIN ANTICOAGULATION DURING PREGNANCY IN PATIENTS WITH MECHANICAL VALVE PROSTHESES

Between January 1987 and December 1989, 20 female patients with one mechanical valve prosthesis (MVP) for at least 1 year postoperatively were studied while on coumarin therapy for the full length of pregnancy. In each case, caesarean section was scheduled for the 38th week. Patients were selected according to the following criteria: (1) prothrombin ratios remaining within the therapeutic range for more than 85% of their total estimations in the previous 12 months with mean daily doses of warfarin less than 5 mg; (2) stable cardiac status; (3) no previous obstetric diseases and (4) full acceptance of the risks involved in the protocol. The patients were in NYHA functional class I or II. Their ages ranged from 23 to 31 years (mean 26 +/- 3). Ten patients had a mitral prosthesis and 10 an aortic prosthesis. Among the 20 mechanical valve prostheses, 10 were Sorin, 6 Starr-Edwards, 2 Bjork-Shiley, and 2 Lillehei-Kaster. Eighteen patients were in sinus rythm, 1 in chronic atrial fibrillation, and 1 had a permanent endocardial pacemaker. Nineteen were delivered by caesarean section: warfarin was withdrawn 48 h before surgery and resumed 24 h thereafter. One patient had premature spontaneous delivery at 36 weeks. The mean prothrombin ratio measured weekly in the 20 patients was 2.06 +/- 0.45 INR, using a mean daily warfarin dose of 4.1 mg +/- 1.63. The mean value of the prothrombin ratio during caesarean section for the 19 patients was 1.23 +/- 0.38 INR. In the 20 live births, the mean birth weight was 2.9 kg +/- 0.40. There were no observed thromboembolic or haemorragic complications, no spontaneous abortions, stillbirths or deaths. All infants underwent cardiac, neurological, X-ray, and echocardiographic examination. No evidence of warfarin embryopathy was found. These findings strongly suggest that (1) the use of strictly controlled coumarin therapy with medium to low doses of warfarin, and (2) delivery by caesarean section may afford pregnant patients with mechanical valve prostheses satisfactory anticoagulation without embryopathy or haemorrhagic complications.