[Heart disease, anticoagulants and pregnancy]

In patients with mechanical prosthetic heart valves, long-term anticoagulant therapy is mandatory to prevent thromboembolic phenomena. Anticoagulation is also necessary in patients with mitral valvular disease and atrial fibrillation. The risk of maternal thromboembolic events is heightened during pregnancy because of the patient's hypercoagulable state. Controversy exists concerning the appropriate treatment of these patients. No method of anticoagulation is risk free. Coumarin derivatives provide adequate protection against thromboembolism and should be used during pregnancy in patients with mechanical prostheses. The administration of coumarin derivatives in the first trimester is associated with an incidence of 26.7% of spontaneous abortion and a risk of 4.1% of coumarin embryopathy. Heparin does not cross the placental barrier and it is the obvious therapeutic alternative. The teratogenic effects of the coumarinics are prevented if these agents are discontinued and replaced by heparin from before the 6th until the end of the 12th week of gestation. However, subcutaneous unfractionated heparin, in the doses that have been employed, does not provide adequate prophylaxis against thromboembolism in these women. In patients treated with heparin, the incidence of spontaneous abortion is similar to that observed when the mothers are treated with coumarin agents. In order to avoid the delivery of an anticoagulated infant, intravenous heparin in full doses, should be substituted for the coumarin agent in the last two weeks of gestation.When anticoagulant therapy is not necessary, the course of pregnancy in women with bioprostheses is similar to that of the general population. However, the short duration of tissue valves is a clear disadvantage for these women