Hearing loss in newborn babies is one of the most common medical issues seen at birth, but without a way to test it, many newborns may go without detection and treatment for months of even years. For this reason, the neonatal hearing screening exists, and is usually completed in the days just after birth. In fact, most babies are screened before leaving the hospital, as testing is recommended no later than one month after birth. An audiologist usually performs the test, and often the newborn sleeps during the neonatal hearing screening.
Infants used to only be tested if they exhibited certain risk factors that often led to hearing loss, but it is now known that a large percentage of newborns without the typical risk factors also suffer from hearing issues. All babies are now tested, usually before leaving the hospital after birth, though of course some risk factors still make some babies more susceptible to hearing loss than others. These factors often include infections that some babies are born with, such as rubella and herpes. A family history of hearing loss during childhood and craniofacial abnormalities also signal a higher chance than normal of neonatal hearing problems. Finally, many babies who stay for at least two days in the neonatal intensive care unit, or NICU, have been found to have higher chances of hearing loss.
Healthcare providers consider the neonatal hearing screening to be crucial because babies who are hard of hearing are often behind their peers when it comes to language and speech. This is especially true in infants whose hearing loss has not been diagnosed by the time they are six months old, since babies learn to talk by listening to others. On the other hand, babies who are diagnosed using the neonatal hearing screening, and then treated by their doctor before six months of age, usually display no speech or language delays at all.
The neonatal hearing screening takes just a few minutes, and most newborn babies sleep during the test. One of the most common ways to test infant hearing involves placing a microphone inside the outer ear canal, which then emits several clicks. In newborns with normal hearing, the hair in the cochlear will echo when they detect sound waves, so this type of neonatal hearing screening measures the echoes to determine whether hearing is normal. Another popular method involves putting earphones around the baby's ears and measuring the brain wave response to several clicks. If the activity in the brain matches what is expected for normal hearing abilities, the newborn has passed the test, while newborns that do not pass are usually retested at a later date.