Between 1974 and 1981, 27 patients became pregnant after prosthetic heart valve replacement with a total of 45 pregnancies. Four pregnancies terminated in therapeutic abortions. Of the remaining 41 pregnancies, 30 were associated with the use of anticoagulants and 11 not. Haemorrhage related to anticoagulant therapy occurred in one patient. The foetal loss in the group with anticoagulant therapy was 33 per cent (10 abortions) and that in the group without was 9 per cent (one abortion). The use of aspirin and dipyridamole during pregnancy (eight pregnancies) did not appear to threaten the outcome of pregnancy. A total of 30 babies were born alive and 20 per cent of them were light for date. There was no perinatal mortality. The typical warfarin embryopathy was not found. Congenital anomalies in four newborns included congenital hydrocephalus, harelip and complete cleft palate, bilateral accessory auricles and bilateral incurving 5th fingers. Subsequently, all except the newborn with congenital hydrocephalus showed normal developmental milestones.