33 Genetic Counseling in Congenital Heart Defects
1. The cardiac abnormalities should be discussed in the context of the other abnormalities detected in the fetus or newborn. For example, the cardiac abnormality may be minor, and yet the overall prognosis can be grim because of major brain abnormalities.
2. In cases with isolated cardiac abnormality or when the extracardiac abnormalities are minimal, the information regarding the prognosis and the surgical procedures should be provided mainly by the cardiologist.
|Single gene disorders||3–5%|
|Maternal disease (IDDM, PKU, SLE etc.)||1%|
|Maternal exposures (infections, teratogens etc.)||1%|
c. This liability has a bell-shaped curve in the general population, where most of the population is in the mean and unaffected, and a small portion of the population past the threshold and expresses the clinical manifestations.
d. This mode of inheritance is the most common cause of genetic disorders and is responsible for the greatest number of patients who will need special care or hospitalization because of genetic diseases, including congenital heart disease.
e. Up to 10% of newborn children express a multifactorial disease at some time in their lives, such as atopic reactions, diabetes, cancer, spina bifida, anencephaly, pyloric stenosis, cleft lip, cleft palate, congenital hip dysplasia, club foot, and congenital heart disease, among others. Some of these diseases occur more frequently in female patients (scoliosis, congenital dislocation of the hips) and some are more common in male patients (pyloric stenosis).
c. Because specific congenital heart diseases are known to be associated with certain chromosome abnormalities, we can assume that the gene or genes associated with these abnormalities must have a major role in cardiac development (Table 33-3).
d. This is emphasized in contiguous-gene disorders where a specific gene known to have a major role in the development of the heart is deleted and results in specific cardiac abnormalities (Table 33-4).