Pulse oximetry, or pulse ox, is a painless, non-invasive
test that measures how much oxygen is in the blood. Infants with heart problems may have low blood oxygen levels, and therefore, the pulse ox test can help identify babies that may have Critical Congenital Heart Disease (CCHD). The test is done using a machine called a pulse oximeter, which is a sensor placed on the baby’s skin. The pulse ox test only takes a couple of minutes and is performed after the baby is 24 hours old and before he or she leaves the newborn nursery.