A 24-year-old woman, who had undergone an aortic valve replacement with a 21-mm St. Jude Medical mechanical aortic valve, wished to have a child. She visited our department because she was aware of the risks associated with pregnancy while undergoing anticoagulant therapy using warfarin potassium. The patient opted to undergo the recommended alternative method involving the use of antiplatelet agents (dipyridamole, ticlopidine, and aspirin) in place of warfarin potassium. Antiplatelet agents were administered while regularly monitoring the platelet aggregability along with the coagulation and fibrinolytic activity. At the 36th week of gestation, antiplatelet agents were discontinued and instead were followed by continuous heparin infusion. A healthy baby was delivered by cesarean section without any complications at the 38th week. Antithrombotic therapy using antiplatelet agents appears to be an effective option for preventing serious problems for pregnant women with a mechanical heart valve.