Risks of Anticoagulant Therapy in Pregnant Women with Artificial Heart Valves

In an attempt to identify the best treatment for pregnant women with cardiac-valve prostheses who are receiving oral anticoagulants, we studied 72 pregnancies prospectively. In 23 pregnancies (Group I), the coumarin derivative acenocoumarol was discontinued and the patients received 5000 U of subcutaneous heparin every 12 hours from the 6th to the 12th week of gestation, in 12 pregnancies (Group II), heparin was not substituted for the coumarin derivative until after the 7th week, and in 37 pregnancies, detected after the first trimester (Group III), the coumarin derivative was given throughout gestation. In most patients heparin was again substituted for the oral anticoagulant after the 38th week. Three mothers had thrombosis of a tilting-disk mitral prosthesis (two cases were fatal) during heparin treatment. No differences were found in the rates of spontaneous abortion in the three groups. Coumarin embryopathy occurred in 25 percent and 29.6 percent of the pregnancies in Groups II and III, respectively. We conclude that in the second and third trimesters of pregnancy, coumarin derivatives provide effective protection against thromboembolism while causing few fetopathic effects, but that these agents are contraindicated from the 6th to the 12th weeks of gestation. Low-dose heparin does not protect against prosthetic-valve thrombosis, and the possibility that a larger dose might be more effective requires further exploration. (N Engl J Med 1986; 315:1390–3.) PATIENTS with artificial heart valves usually require long-term anticoagulant therapy with coumarin derivatives to prevent thromboembolic phenomena. 1 This is particularly true during pregnancy, when there is a hypercoagulable state 2 , 3 and the mother has an increased risk of systemic embolization and death. 4 , 5 The antiplatelet agents dipyridamole and aspirin do not provide adequate protection against thromboembolism in this situation. 4 On the other hand, the use of coumarin derivatives during pregnancy carries serious risks to the fetus, such as coumarin embryopathy and death, especially if the drugs are administered during the first trimester. 4 , 6 7 8 9 It has been suggested that the teratogenic effects may develop . . .