Risk factors

In most cases, the exact cause of a congenital heart defect, such as pulmonary atresia, is unknown. However, several factors may increase the risk of a baby being born with a congenital heart defect, including:

• A parent or sibling with a congenital heart defect
• A mother who is obese before getting pregnant
• Smoking before or during pregnancy
• A mother who has poorly controlled diabetes
• Use of some types of medications during pregnancy, such as certain acne drugs and blood pressure medications