Causes and Risk Factors

What are the causes and risk factors of congenital heart disease?

The causes of congenital heart disease often are not known, but genetic and environmental factors may play a role.

According to the March of Dimes, in most cases scientists do not know what causes hearts to be developed abnormally.1 It does appear that genetics and the environment play a role, but exactly how is uncertain.

  • Genetics: Some heart defects have a clear genetic link, such as Long QT Syndrome. Since the 1990s, nearly 10 gene mutations (changes) that can cause isolated heart defects have been identified.2
  • Viral: One particular virus, rubella (German measles), can cause heart defects if a woman contracts the disease the first three months of a pregnancy.
  • Heredity: For example, a parent who has a congenital heart defect may be more likely than other people to have a child with the condition. In rare cases, more than one child in a family is born with a heart defect.
  • Chronic illness: Certain chronic illnesses in the mother, such as diabetes, may contribute to heart defects.1 However, women with diabetes can reduce their risk by making sure their blood sugar levels are well controlled before becoming pregnant. 

Did you know?

There are at least 35 distinct types of congenital heart defects including Ventricular Septal Defect (VSD), valvular abnormalities, and abnormal connections among the veins, heart, and great arteries.2