Abnormal newborn screening simply refers to standard blood tests that are performed on newborn children in order to detect any unseen genetic conditions or diseases that may require early medical intervention in order to prevent harm to the baby. When such tests reveal an abnormal result, additional testing must be done to arrive at a diagnosis; in many cases, babies who have an abnormal initial screen are found to have normal results upon follow-up testing. In all, abnormal newborn screening can help detect up to 60 different diseases by looking at the amounts of different substances in the blood that are associated with those conditions. This testing is performed by pricking the baby’s heel and collecting a blood sample shortly after birth. Additional aspects of newborn screening include a hearing test and pulse oximetry to determine oxygen levels in the baby’s hand and foot. Because newborn screening is considered a public health service, it is performed on all babies born in the United States except in cases where parents decline the testing for religious reasons.