Heart disease during pregnancy necessitating cardiac surgery is potentially increasing maternal and fetal morbidity and mortality. Most patients know about their heart disease long before conception however the relation between the deteriorating cardiac function and the perinatal complications is not emphasized. Best possible results can be achieved by providing preconception counseling for cardiac patients. Consequently, heart-surgery can be performed before pregnancy thereby the maternal risk is lower and fetal loss or induced abortion can be avoided. The pregnant state is not optimal for cardiac surgery as the principal interest of the mother and the fetus is different. Cardiac surgery should be reserved only for saving the patient's life when medical therapy proves insufficient or when conservative management leads to acute heart failure. The multidisciplinary approach, correct risk assessment, diagnosis, operative indication, timing along with appropriate anaesthesia, extracorporeal circulation and alert monitoring of the uterine activity and fetal heart rate patterns make the intervention technically safe. Fetal monitoring is inevitable for prompt correction of operative conditions in case of impending hypoxemia. The perioperative fetal risk can be reduced by applying normothermia, high mean arterial pressure and cardiac index during the intentionally shortest intervention. Cardiac operation with cardiopulmonary bypass during pregnancy has become a relatively safe procedure for the mother but not for the baby.