Pregnancy with mechanical mitral prosthesis poses several risks either for the fetus and the mother. A good care including the contribution of an obstetrician, a cardiologist, an anesthesiologist and a neonatologist is strongly recommended during pregnancy until delivery. The anticoagulation causes a major risk. The heparin may be given during the whole pregnancy or may be replaced by the oral anticoagulants from the 13 weeks of last menstrual period until 10 to 15 days before delivery. Considering the difficulty to have an adequate anticoagulation with subcutaneous heparin, we have tried in ambulatory with our patient the intravenous heparin under a strict observation.