Hypoplastic left heart syndrome

The best time to learn about genetic risks and testing options is before pregnancy. Assessing risks in families affected by congenital heart disease (CHD) is a complex process that takes into account the affected family member's heart defect, medical history, physical and other characteristics, as well as the family medical history.  In general, people who may benefit from preconception genetic counseling for CHD include:^[1]

Adults who have CHD, to learn more about risks to their children
Parents of a child with CHD, to learn more about risk to siblings
People with a strong family history of CHD
People with signs and symptoms of a genetic syndrome associated with CHD, such as distinct facial characteristics, birth defects, learning impairment, behavioral and/or psychiatric disorders
People with types of CHD known to occur in association with a genetic condition, such as 22q11.2 deletion 

When genetic testing is available, testing typically begins with the family member who has CHD when possible. Testing on this individual has the greatest likelihood of finding a genetic cause for CHD. Currently clinical genetic testing is available for only select causes of CHD. Most cases of isolated CHD are thought to be sporadic and informative genetic tests are not readily available. If you are unsure if your son would benefit from genetic counseling, we encourage him to speak with his healthcare provider.

In addition, you may find the following article to be a helpful resource. The article provides a comprehensive overview of healthcare decisions and testing considerations couples can make to help ensure a healthy pregnancy. 

Brundage SC. Preconception Health Care. American Family Physician. 2002 Jun 15;65(12):2507-2515.

HLHS typically occurs sporadically (randomly), in otherwise normal babies with no family history of HLHS.^[2] In a few children, isolated HLHS is known to be genetic. These cases may be due to mutations in the GJA1 gene with autosomal recessive inheritance, or the NKX2-5 gene with autosomal dominant inheritance.^[3][4]

Most congenital heart defects are thought to be caused by interactions between unidentified genes and the environment. This is called multifactorial inheritance. When the specific cause of isolated HLHS in a child is not known, the recurrence risk of left heart disease in first degree relatives of infants with HLHS is estimated at 2 to 4 percent.^[2]

HLHS has also been reported with certain genetic disorders including Turner syndrome, Jacobsen syndrome, trisomy 13, and trisomy 18.^[2]

To find a medical professional who specializes in genetics, you can ask your doctor for a referral or you can search for one yourself. Online directories are provided by the American College of Medical Genetics, and the National Society of Genetic Counselors. If you need additional help, contact a GARD Information Specialist. You can also learn more about genetic consultations from Genetics Home Reference.