Answer:
The cause of congenital heart disease is still unknown. However, there are studies that show a link between congenital heart disease and: smoking while pregnant, obesity while pregnant, and some drugs including Wellbutrin (an antidepressant). A history of heart disease in your family can also be a factor.
Follow your obstetrician's advice for a healthy pregnancy. This will increase your chances for a healthy baby. However, not all causes of heart disease are known. Your baby might still be born with a heart defect. Ask for a (completely painless) pulse/ox test before your baby leaves the hospital. Detecting congenital heart defects before checking out of the hospital saves lives.