Patients with artificial valve prostheses require lifelong anticoagulation treatment. The risk of thrombotic complications increases greatly in pregnancy. Anticoagulant treatment in pregnant women with artificial heart valve prostheses in one of the most controversial problems in medical practice as anticoagulants which are beneficial and safe for the mother may by hazardous for the fetus. Recommended procedure is to administer heparin subcutaneously at last during the first 14 weeks and the last 2 weeks of gestation and coumarin derivates throughout the second and third trimesters. In asymptomatic or mildly symptomatic women who are willing to follow a strict regimen of antithrombotic prophylaxis in pregnancy the risk is not associated with an increased morbidity or mortality in the mother or fetus. Hence, recommendations against pregnancy in women with artificial heart valves are not always justified.