A series is presented of 7 women who underwent cardiac valve replacement and who ultimately became pregnant. The only infant death was that of a premature baby whose mother received oral anticoagulants until delivery. The remaining 6 babies were normal and survived. One mother died suddenly on the fourth postpartum day and was found to have a periprosthetic clot on postmortem examination. Although a certain risk exists for the fetus whose mother receives oral anticoagulants since they cross the placental barrier, this risk is far lower that that for the mother who does not receive anticoagulation. From a prospective point of view, it would appear preferable to use prostheses such as the porcine heterograft that do not necessitate the administration of anticoagulants.