[Heart disease, pregnancy and anticoagulant therapy]

Pregnancy is a hypercoagulable state. Some women with cardiac disease and mechanical valve prosthesis are at increased risk of arterial thromboembolic phenomena. These women are maintained on oral anticoagulants and require effective permanent prophylaxis during pregnancy. The use of oral anticoagulants during pregnancy is controversial because of the risks of embriopathy (Chondrodysplasia punctata) in fetuses who are exposed to coumarin between the 6th and 9th week of gestation, the risk of neurological disorders all through pregnancy, and a higher incidence of abortion and stillbirths. The exact incidence of these complications is unknown. Most of this information comes from North American reports, when much higher mean daily doses of coumarin were administered, and they were probably overemphasised. Reports from Europe, Asia and our own, show that both embriopathy and central nervous system malformations are probably dose-related and that the risks of abnormality to the fetus are small. The ACC Antithrombotic Consensus (1998) recommends the use of subcutaneous heparin all through pregnancy or until the 13th week of gestation. Heparin does not cross the placenta, however there is a higher risk of maternal bleeding, abortion and stillbirths. With the use of small dose of heparin and of therapeutic heparin doses there is a risk of prosthesis thrombosis. Anticoagulant treatment of patients with prosthetic heart valves during pregnancy remains controversial. Subcutaneous heparin prophylaxis is feasible but the use of well controlled oral anticoagulants appear to offer lower risks of maternal and fetal complications.