Testing for congenital heart defects can be done while a woman is pregnant or after a baby's birth.

A fetal echocardiogram, which can be done as early as 16 weeks of pregnancy, is the best test before a baby's birth. The test uses sound waves to take pictures of the fetal heart. The fetal echocardiogram may be done if:

• You have a family history of heart defects.
• You have been exposed to certain chemicals during your pregnancy.
• You have taken medicines during your pregnancy that may increase the risk that your baby (fetus) will develop heart defects.
• A fetal ultrasound shows a problem with the heart. This routine test is often done during pregnancy. Fetal ultrasound can show a problem with the heart's structure, but it may not show some kinds of heart defects.

Many congenital heart defects are found within the first month after a baby is born. To diagnose a heart defect, a doctor will ask questions about the baby's symptoms, appetite, and other habits and give the baby a physical exam. An echocardiogram and possibly a heart catheterization (angiogram) may be needed.

More tests may be needed, depending on the symptoms and type of defect. These may include:

• Chest X-ray, to check the size and blood vessels of the heart.
• Electrocardiogram (ECG, EKG), to check for irregular heart rhythms (arrhythmias) that may be related to a congenital heart defect.
• Stress test (exercise electrocardiogram), which may be done around the time the child starts school to find out how much exercise your child can do.
• Blood tests, to check for anemia, polycythemia, or levels of certain chemicals in the blood.
• Oximetry, to see whether oxygen-poor blood is being pumped to the body. This test would be done if your baby has severe difficulty breathing or has a bluish tint (cyanosis) to the skin, lips, and nail beds. The amount of oxygen in the blood can also be measured by an arterial blood gas (ABG) or a transcutaneous monitor (in infants).
• MRI of the heart and major blood vessels, to view abnormal heart structures and/or blood vessels. If this test is done, your child will probably be given medicine to make him or her relax and sleep during the test.

Early Detection

In families with a history of congenital heart defects, genetic testing may be done.

A baby may be checked for congenital heart defects if the mother:

• Had rubella during pregnancy.
• Has diabetes or phenylketonuria.
• Has a congenital heart defect.