The ability to hear is fundamental for a child’s development, especially for speech and language acquisition. Early detection of hearing loss in newborns is important because timely interventions can significantly improve a child’s communication skills and overall well-being.
Prevalence of Hearing Loss at Birth
Congenital hearing loss refers to hearing impairment present at birth and is among the most common conditions found in newborns. Approximately 1 to 3 out of every 1,000 babies are born with some degree of detectable hearing loss. Worldwide, the prevalence is estimated at about 1.5 per 1,000 newborns. In the United States, around 6,000 infants were identified with permanent hearing loss in 2022. This indicates that a significant number of infants are affected.
Identifying Hearing Loss in Newborns
Newborn hearing screening programs are standard practice in many hospitals, designed to identify hearing loss shortly after birth. These screenings are safe, quick, and typically performed while the baby is asleep. Two primary methods are used for these screenings: Otoacoustic Emissions (OAEs) and Automated Auditory Brainstem Response (AABR).
OAE tests involve placing a small probe in the baby’s ear canal to play sounds and record the echoes produced by the inner ear. If the cochlea is functioning normally, it generates an echo, indicating that sound is being processed. The AABR test uses electrodes placed on the baby’s head to measure how the auditory nerve and brainstem respond to sounds played through earphones. This test assesses the entire auditory pathway from the ear to the brainstem.
These screenings are important because early detection allows for interventions before three months of age, which can significantly improve speech and language development outcomes. Infants who do not pass the initial screening are referred for more comprehensive diagnostic evaluations to determine the nature and extent of any hearing loss.
Common Causes of Congenital Hearing Loss
Congenital hearing loss can stem from a variety of factors, broadly categorized into genetic and non-genetic causes. Genetic factors account for over 50% of all congenital hearing loss cases. These can be syndromic, meaning hearing loss occurs as part of a broader set of symptoms (e.g., Down syndrome, Usher syndrome), or non-syndromic, where hearing loss is the only symptom.
A significant genetic cause is mutations in the GJB2 gene, which encodes the connexin 26 protein. This gene is responsible for up to 50% of inherited, severe-to-profound non-syndromic hearing loss. This mutation is common in certain populations.
Non-genetic causes include infections, prematurity, and certain medications. Congenital cytomegalovirus (CMV) infection is a leading non-genetic cause of hearing loss in children. Premature birth also increases the risk of hearing loss, with preterm infants being more susceptible due to multi-system illnesses and exposure to medications that can harm the auditory system. Exposure to certain ototoxic medications during pregnancy or shortly after birth can contribute to congenital hearing impairment. Other non-genetic factors include low birth weight, oxygen deprivation at birth (asphyxia), severe jaundice, and complications during delivery.