Genetic Counseling
Genetic Counseling for Adults With Congenital Heart Disease
Two of the most common questions after the birth of a child with a heart defect are: “Why did this occur?” and “What’s the risk of having more children with heart defects?” These same questions arise when a person with congenital heart disease considers starting a family. Evaluating this risk is part of genetic counseling.
Cause of Congenital Heart Disease
The heart is one of the earliest organs to completely form in a fetus. This allows blood to be pumped to the developing embryo. The heart is completely formed by about eight weeks after conception. Heart development involves a number of complex steps that must occur at certain times. When these don’t occur, a wide variety of defects can result. Much remains unknown about the exact origin of most heart defects, but many known factors might be related to them.
Maternal Factors
The mother’s good health affects the infant’s overall well-being. It can influence such things as premature delivery and the size of the baby. But birth defects of the heart may occur despite good health and a normal pregnancy. Mothers often may feel guilty that they caused the child’s defect. Usually this isn’t the case. However, maternal illnesses such as diabetes have been linked to a slightly increased incidence of birth defects, including heart defects.
People with congenital heart disease are at greater risk of having a child with a heart defect. This is true whether the affected person is the father or the mother. The frequency of disease increases from less than 1 percent in the general population to 2-20 percent when a parent is affected. There also seems to be a difference depending upon the nature of the parent’s defect. Defects such as coarctation of the aorta or aortic valve stenosis have the greatest risk of occurring in the child. Each time another close family member is also affected, the risk increases even more.
Chromosomal Factors
Most people with congenital heart disease have normal chromosomes. People with Down syndrome (trisomy 21) and other chromosomal anomalies such as other trisomies or Turner’s syndrome, have a high incidence of heart defects related to their syndrome. If they can conceive, these people can expect their offspring to have a high likelihood of the same syndrome and heart disease.
There are more subtle chromosomal abnormalities, such as 22q11 deletion (Di George syndrome), that are just now being discovered. These may significantly affect the ability to predict the presence of heart disease in some people.
As the science of genetics and our ability to understand and define the genetic code improves, more definite answers to the genetics of congenital heart disease may be revealed.
Exposure to Substances
A mother’s exposure to certain prescription medications, industrial chemicals or solvents, ionizing radiation (X-ray), alcohol, viral infections such as rubella (German measles), and possibly recreational drugs, leads to a higher incidence of heart disease. Often the particular exposure and its risk are known. Yet, this is a particularly difficult area for predicting how big the risk is. It may depend upon the extent of exposure, timing of exposure relative to the pregnancy and unknown maternal factors that make some people more susceptible to a particular agent. That’s why you should avoid these potentially toxic agents.
Genetic Counseling
In most cases, having congenital heart disease shouldn’t stop you from having a family. But realize that you’re at greater risk for having children with heart defects, and that if defects occur, they’re most often like your own. The severity of the defect may vary, and this may have a profound impact on the child. Further testing, such as chromosome analysis before pregnancy or amniocentesis during pregnancy, may be recommended. Most often a fetal echocardiogram done by a specialist such as a pediatric cardiologist familiar with imaging congenital heart disease will be indicated.