There are two questions frequently asked by the parents of children born with a congenital heart disease: "why our son came to life with a heart malformation?" "did we done something wrong that produced our child's heart defect?".

Actually the knowledge about the causes of the congenital heart diseases can be summarized in four points:

1. about 8% represents one aspect of a more important disease due to chromosomes impairing early during pregnancy. The most common chromosomal abnormality is the Down Syndrome due to the presence of three chromosomes 21 instead of two. The incidence of Down syndrome is about 1/700 born of which 45% have a congenital heart disease.

2. In other cases the number of chromosomes is normal but one or more genes presents on the chromosomes are impaired and produce a disease that include heart defects in the features.

3. In other cases the heart disease is produce by the exposure of the embryo to teratogenic agents. Rubella during the first quarter of pregnancy is a teratogenic agent because in a lot of cases provokes heart defect in the fetus generally associated with defects in other organs. Exaggerated consumption of alcohol, mother exposure to virus infections, radiations or particular chemicals can be of teratogenic effect. Even maternal diabetes increases the possibility of having heart defects in the newborn. The fetus will develop a heart defect only if the exposure to teratogenic agents occurs early the pregnancy because heart forming happens during the first quarter.

4. In most of cases the heart defect occurs for unknown reasons. It means that it is impossible to prevent the occurrence of congenital heart diseases. Former cases in family are not fundamental but can be of some importance. In a couple with a child affected of congenital heart disease the risk of having others increases: generally if the risk is about 1%, in a couple with a child affected the risk can rise up to two or three time. The risk is a little bit higher if one of the parents has a heart disease.

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