Universal Newborn Hearing Screening (UNHS) is performed shortly after birth to identify hearing differences early, which is beneficial for a child’s speech and language development. A “fail” result, also called a “refer,” simply means the baby needs a closer look, not that they have a permanent hearing loss. For a failure isolated to a single ear, the outcome is overwhelmingly positive, with the vast majority of babies passing a follow-up test. This is an extremely common first step in ensuring a baby’s hearing is properly assessed.
Why Initial Screening Failures Are Common
A failure on the first newborn hearing screening is common, affecting between 2% and 10% of all babies screened in the United States. The initial screening tests are designed to be highly sensitive, meaning they cast a wide net to ensure no case of actual hearing loss is missed. This high sensitivity, however, results in a significant number of false-positive results, where a baby fails the screen but has normal hearing. For the Otoacoustic Emissions (OAE) test, the false-positive rate can range from 5% to 21% in the first three days of life because the test is sensitive to any obstruction in the ear. The initial result is only a screening, which sorts babies into “pass” or “refer,” and a “refer” is not a medical diagnosis of permanent hearing loss.
Temporary Factors Causing the One-Ear Failure
The most frequent reason for a one-ear failure is a temporary blockage in the outer or middle ear. During the birthing process, fluid and debris can enter the ear canal and the middle ear space. Specifically, residual amniotic fluid, vernix, or blood can obstruct the passage of sound waves needed for a clear test result. This temporary issue causes a conductive hearing difference, which prevents sound from traveling efficiently to the inner ear, often presenting as a unilateral failure since the fluid may clear from one ear faster than the other. Other non-medical factors, such as the baby being restless, crying, or movement during the test, can also interfere with the precise measurement of the equipment, leading to an inaccurate result.
The Follow-Up Process and Next Steps
Following an initial failure, the next step is a rescreening, generally recommended before the baby reaches one month of age. This allows time for any residual fluid or debris to clear from the ear canal and middle ear. Hospitals sometimes wait 12 to 24 hours after birth before the initial screening to reduce the likelihood of a fluid-related false-positive result. If the baby fails the second screening, they are referred for a comprehensive diagnostic evaluation, which should be completed by three months of age. This detailed testing is typically performed by a pediatric audiologist and involves the Auditory Brainstem Response (ABR) test, which is considered the gold standard for diagnosis, providing a more precise picture of hearing function.
When a Failure Signals Actual Hearing Loss
While most initial failures are temporary, the screening program exists to identify the small percentage of babies with actual hearing loss. Approximately one to three out of every 1,000 babies are born with some degree of permanent hearing loss. Hearing loss is classified as either conductive, involving the outer or middle ear, or sensorineural, involving damage to the inner ear or the auditory nerve. Sensorineural hearing loss is often permanent and can be caused by genetic factors, which account for 50% to 60% of cases, or non-genetic risk factors like premature birth, low birth weight, maternal infections (CMV), and an extended stay in the NICU. When diagnostic testing confirms a permanent hearing loss, early intervention is immediately initiated, which has been shown to significantly improve a child’s long-term speech and language developmental outcomes.