Congenital heart disease (CHD) is among the most common congenital abnormalities and involves structural anomalies of the heart and/or related major blood vessels. Congenital heart disease arises in the fi rst trimester of pregnancy, occurring often and in many forms. The reported CHD birth prevalence rate ranges from 6 per 1,000 newborns in the Netherlands to 9 per 1,000 newborns in the United States of America. This percentage is much higher if fetal deaths are taken into account.3 CHD is the leading cause of infant mortality4 and contributes to 30% to 40% of all deaths during infancy and early childhood. The morbidity varies with the severity of the CHD and can be quite serious and life threatening. The multiple surgeries needed to correct the anatomical defects can be debilitating. Furthermore, the quality of life of these patients is often compromised due to severe physical as well as psychological problems. Having a child with CHD is also a source of great concern for parents and signifi cantly affects the quality of life in the families as well. Moreover, in 1992 the estimated average lifetime cost of the most clinically important CHD ranged from $262,000 to$505,000 per new case in the United States of America. Over the past decades the diagnosis, medical care and surgery have considerably improved the prospects for children with CHD and resulted in a signifi cant decrease of CHD mortality and morbidity. Nowadays approximately 85% of children with CHD survive. Therefore, the primary prevention of CHD would be a big step forward, being only possible when more insight is gained into the embryogenesis of the heart and the role of genes and environmental factors.