Women with important cyanotic or uncyanotic, operated or unoperated congenital heart disease (CHD) have been shown to carry an inherent risk during pregnancy for themselves and for their fetus. Obstetrical and fetal echocardiography has recently been upgraded by new technical developments in ultrasound machines. These improvements have increased the detection rate of congenital malformations and cardiac anomalies which ranged in the past between 4 and 60% for significant anomalies. Obesity or an unfavourable position of the fetus may, however, obscure the imaging quality and cause limitations to visualise the fetal heart from different angles and thus prevent the detection of anomalies. In addition, several cardiac anomalies develop throughout pregnancy and may not yet be present at an early date of screening. While the risk for a congenital cardiac malformation (CCM) in a normal population is 0.8-1%, the recurrence rate for CCM increases to 2 to 3% when a previous child has been affected but will become significantly higher when genetically determined anomalies have affected a family member or when the pregnant woman (5.8%) has CHD. The aim of fetal screening in women with CCM is to ascertain normal intrauterine growth, to exclude fetal CHD and/or to ascertain a malformation or arrhythmia which has been suspected during an obstetrical screening. The acquired detailed echocardiographic knowledge of the malformation or arrhythmia allows the explanation of a CCM to the future parents, to present therapeutic options during pregnancy or after birth and to plan delivery in a tertiary center that provides early cardiovascular and/or catheter interventions and disposes of intensive care facilities for affected newborns. Under certain conditions, termination can be discussed in early pregnancy. Very recent publications have shown how important a prenatal diagnosis can become in a new-born with transposition of the great arteries and a very restrictive foramen ovale (Circulation 1999). Therapeutic measures in the fetus have been attempted with very limited success so far; successful life saving treatment does, however, exist for fetal arrhythmias.