Newborn screening tests take place before your newborn leaves the hospital. Babies are tested to identify serious or life-threatening conditions before symptoms begin. Such diseases are usually rare. However, they can affect a baby's normal physical and mental development. Most tests use a few drops of blood from pricking the baby's heel. A hearing test involves placing a tiny earphone in the baby's ear and measuring his or her response to sound. If a screening test suggests a problem, your baby's doctor will follow up with further testing. If those tests confirm a problem, the doctor may refer you to a specialist for treatment. Following your doctor's treatment plan can save your baby from lifelong health and developmental problems.