How is newborn screening done?

Newborn screening usually begins with a blood test 24 to 48 hours after a baby is born, while he or she is still in the hospital. In some states, a second blood test is performed at a check-up appointment with the baby's pediatrician when the baby is 1 to 2 weeks old. Newborn screening is part of standard care; parents do not need to request to have the test done.
The test is performed by pricking the baby's heel to collect a few drops of blood. There are very few risks associated with this procedure, and it involves minimal discomfort to the baby. The blood is placed on a special type of paper and sent to a laboratory for analysis. Within 2 to 3 weeks, the test results are sent to the baby's doctor's office or clinic.
If a baby is born outside a hospital (for example, at home or in a birthing center), a doula or midwife may collect the blood sample needed for the newborn screening test. Otherwise, the required testing can be performed at the baby's doctor's office or at a hospital.
In addition to the blood test, most states also screen newborns for hearing loss and critical congenital heart disease. These tests are also done shortly after birth. The hearing test uses earphones and sensors to determine whether the baby's inner ear or brain respond to sound. The test for critical congenital heart disease, called pulse oximetry, uses a sensor on the skin to measure how much oxygen is in the blood. Low oxygen levels suggest that an infant may have heart problems. The hearing and pulse oximetry tests are painless and can be done while the baby is sleeping.