Risk factors

Most congenital heart defects result from problems that occur early as the baby's heart is developing before birth. The exact cause of most congenital heart defects is unknown. However, certain environmental and genetic risk factors may play a role. They include:

• Rubella (German measles). Having rubella during pregnancy can cause problems in your baby's heart development. Your doctor can test you for immunity to this viral disease before pregnancy and vaccinate you against it if you aren't immune.
• Diabetes. A woman who had diabetes before getting pregnant can reduce the risk of congenital heart defects by carefully controlling blood sugar before and during pregnancy. Diabetes that develops during pregnancy (gestational diabetes) generally doesn't increase a baby's risk of developing a heart defect.

• Medications. Certain medications taken during pregnancy may cause birth defects, including congenital heart defects. Give your doctor a complete list of medications you take before trying to become pregnant.

  Medications known to increase the risk of congenital heart defects include thalidomide (Thalomid), angiotensin-converting enzyme (ACE) inhibitors, statins, the acne medication isotretinoin (Absorica, Amnesteem, others), some epilepsy drugs and certain anxiety drugs.

• Drinking alcohol during pregnancy. Drinking alcohol during pregnancy increases the risk of congenital heart defects.
• Smoking. If you smoke, quit. Smoking during pregnancy increases the risk of a congenital heart defect in the baby.
• Family history and genetics. Congenital heart defects sometimes run in families (are inherited) and may be associated with a genetic syndrome. Many children with an extra 21st chromosome (Down syndrome) have heart defects. A missing piece (deletion) of genetic material on chromosome 22 also causes heart defects.