Risk factors

While the exact cause of congenital heart defects, such as truncus arteriosus, is unknown, several factors might increase the risk of a baby being born with a heart condition. These include:

• Viral illness during pregnancy. If a woman contracts rubella (German measles) or another viral illness during early pregnancy, the risk of congenital heart defects in her baby is increased.
• Poorly controlled diabetes during pregnancy. Diabetes that isn't well-managed can increase the risk of birth defects, including heart defects.
• Certain medications taken during pregnancy. Many medications aren't recommended for use during pregnancy because of potential risks to the fetus.
• Certain chromosomal disorders. Children with DiGeorge's syndrome or velocardiofacial syndrome have an increased risk of truncus arteriosus. These conditions are caused by an extra or defective chromosome.
• Smoking during pregnancy. Continuing to smoke while pregnant increases the risk that the baby will be born with a heart defect.
• Alcohol use. Women who drink alcohol during the first trimester of pregnancy increase their risk of having a baby with a congenital heart defect. Men who drink alcohol also contribute to their baby's congenital heart defect risk.
• Obesity. Women who are obese can have an increased risk of having babies with congenital heart defects.