The search for a safe and effective anticoagulation regimen in pregnant women with mechanical prosthetic heart valves.

Warfarin, a time-honored treatment for nonpregnant patients with MPHV has been also shown to be effective in the prevention of thromboembolic complications during pregnancy (1–3). Exposure to warfarin in the first 6 to 12 weeks of pregnancy, however, can be associated with a significant risk to the fetus, including spontaneous abortions and warfarin embryopathy (1,3). In addition, the use of oral anticoagulation therapy during pregnancy may also be associated with fetal hemorrhage, including intracranial bleeding (4), central nervous system abnormalities, and minor neurologic dysfunction and low intelligent quotients in later age (1). Although a number of recent studies have reported no untoward effects with the use of warfarin during pregnancy (5–7), others have clearly shown a high and unacceptable rate of fetal complications (8–13). Because of these risks, both women and physicians have been reluctant to use oral anticoagulation during the first trimester or at any time during pregnancy.