Question:
I had a child with a congenital heart defect; why did this happen? What is the likelihood of my having another child with the same defect or a different defect?

Answer:
Heart defects, especially those occurring as isolated problems in otherwise healthy infants, generally do not have readily identifiable genetic or environmental causes. This had led to the theory that an abnormal interaction between the genetic code and the environment in which the fetus develops results in abnormal heart development. As the circulatory system is one of the first organ systems to begin functioning, blood flow problems occurring early fetal life can be compounded as the fetus develops.

Slightly less than 1percent of infants born in the U.S. (about 8 per 1,000 live births) have a congenital heart defect. Depending on the defect, the chances of a sibling also being born with the same defect or other heart defect are about 2 percent to 3 percent. While this is higher than the general population rate of 0.8 percent, it is still a relatively small chance. Relatively few genetic defects causing particular heart defects have been found. However, some defects have a gender predominance. For example, one common defect, patent ductus arteriosus, occurs more commonly in girls. Also, several genetic syndromes (such as Down syndrome) have cardiac malformations as well defects in other organ systems. About 25 percent of children with a heart defect have one or more additional cardiac or non-cardiac abnormalities. These facts all point to a genetic component to the occurrence of congenital heart defects.

Numerous environmental exposures are also associated with congenital heart defects. These include using some medications for seizures, acne, or bipolar psychiatric disorder, or having some diseases such as rubella (German measles), other viral diseases, diabetes or lupus early in pregnancy. Alcohol and street drugs may increase the risk also, as can exposure to chemicals such as certain pesticides and solvents.

Congenital defects are not that common. They are not likely to occur in future children, although this does sometimes happen. Remaining healthy and avoiding certain exposures is helpful. If you or your partner do become pregnant again, it will be important to tell your obstetrician about your other child. Fetal echocardiograms (ultrasounds) may help detect problems as early as mid-pregnancy.