the exact cause of most heart defects is still unknown. Although the reason defects occur is presumed to be genetic, only a few genes have been discovered that have been linked to the presence of heart defects. So they’re likely due to a combination of multiple genetic and environmental factors.
Some people with congenital heart defects have a specific genetic condition that can include other health problems. They may or may not know that they have such a condition. The chance for their child to also have this condition can be as high as 50%.
Rarely, congenital heart defects are caused by changes in a single gene. Often when this is the case more than one person in the family has a heart defect. The chance for another family member to have a heart defect can be as high as 50%.
Heart defects can also be caused by something your mother was exposed to in her pregnancy, such as an infection or a drug. In this case, the chance that your children will have heart defects is no higher than that of the average person.