When faced with this question from parents of children with congenital heart disease, it is sometimes really difficult to explain it in one or two sentences. There are many causes of congenital heart disease: spontaneous mutations of genes in the body; mutations inherited from the parents; changes due to external or environmental influences; and a combination of these factors. In fact, two different children with the same heart condition may have completely different causes. Genetic disorders can lead to heart disease alone or to a syndrome that encompasses heart disease, a syndrome that can affect the body, its organs and functions in different ways. In some cases, heart disease may be the first sign that a patient is suffering from a certain syndrome. Therefore, if a child has a heart condition, it should be determined whether the child has a certain syndrome and the heart condition is only part of this syndrome. Down syndrome, for example, is caused by an extra chromosome 21, which means that three chromosomes 21 are present, hence the name 21-3 syndrome. The trisomy variant is caused by an error in cell division. The most common concomitant congenital heart defects that occur in Down syndrome are atrial septal defect (endocardial cushion defect), tetralogy of Fallot, interrupted aortic arch, and ventricular septal defect. The incidence of congenital heart disease is 10 to 14 times higher in siblings and children of patients with congenital heart disease than in the general population; if the parents are healthy and the first child has congenital heart disease, the likelihood of the second child having the disease is 1 to 6%; if the parents are healthy and two consecutive children have congenital heart disease, the likelihood of having another child with congenital heart disease increases to 10%; if the first child has the disease and either parent also has the disease, the risk of the second child having the disease increases to If the first child has the disease and either parent also has the disease, the risk of the second child increases to 3-18%. In conclusion, genetic predisposition is only one of the causes of precocious heart disease, and the mechanism is not completely understood.