Congenital heart diseases are malformations of the heart and the large blood vessels arising from it. They are the consequence of abnormal development of the organ while a baby is in the uterus. About 6-8 babies in every 1000 are born with congenital heart diseases. Many heart defects are relatively mild and do not require treatment. For children with significant heart lesions majority of them can be managed by medications, interventional cardiac catheterisation and cardiac operations. In only very small number of babies the heart defects are so severe that they are considered as inoperable, and the babies may die soon after birth.
Causes
In most cases the congenital heart defects are unknown but there are two major factors influencing the development of fetal heart:
(1) Genetic factors
The development of all fetal organs is controlled by genes. Theoretically there should be an explanation to each case of congenital heart disease from the genetic point of view. However the link between genes and congenital heart malformation is very complicated, and is not well understood by scientists. Therefore for majority of patients it is still not possible to identify the exact genetic mechanism.
In some cases there may be a family history of similar heart problems, for example, one of the parents or siblings may have congenital heart defects. This is a signal that genetic influence is strong in that particular family with congenital heart defects. Still it does not mean that the genes responsible for the disease are known.
We know that children suffering from certain genetic disease such as Down's syndrome, which is caused by presence of an extra chromosome 21, have higher chance of having congenital heart defects. Again the mechanism of how an extra chromosome can modify the fetal heart development is far from clear.
(2) Environmental factors
These are extrinsic influence on the development of fetal hearts. They are often the results of maternal drug taking and maternal illness during pregnancy, usually in the first trimester when the fetal heart development is most critical. German measles that the mother has had while pregnant is well known to cause pulmonary stenosis, and also eye and brain defects. Certain drugs such as thalidomide, alcohol, radiation during pregnancy increase the risk of developing congenital heart disease and should be avoided if possible.
