Is It Common for a Newborn to Fail a Hearing Test in One Ear?

Failing a newborn hearing screen in one ear is common and, in most cases, does not mean your baby has permanent hearing loss. Somewhere around 2 to 10 percent of all newborns do not pass their initial screening, and a large share of those failures involve just one ear. The majority turn out to be false positives caused by fluid or debris in the ear canal that clears on its own within days or weeks. A smaller number of babies do have a genuine unilateral hearing loss that needs attention, but even that is more manageable than many parents expect.

How Often Newborns Fail in Just One Ear

Most hospitals screen every baby’s hearing before discharge, testing each ear separately. It is entirely normal for one ear to pass and the other to come back as “refer,” meaning the test could not confirm normal hearing on that side. In one screening program that tracked over 41,000 infants, about 2,700 failed the initial screen. Among those who completed follow-up evaluation, unilateral findings were common: 19 babies had permanent sensorineural hearing loss in one ear, while 18 others had conductive hearing loss on one side, often from fluid.¹ In a separate study of high-risk newborns who failed screening, roughly half failed in just one ear rather than both.²

One detail that surprises many parents: the left ear fails more often than the right. A study examining initial OAE (otoacoustic emissions) screening found that about 1.5 percent of newborns failed solely in the left ear, compared with only 0.3 percent in the right.³ The reasons for this asymmetry are debated, but the practical takeaway is that a one-sided failure, especially on the left, is an everyday event in newborn nurseries.

Why Most One-Ear Failures Are Temporary

Newborn hearing screens are designed to be sensitive rather than specific. That means they catch every baby who might have a hearing problem, at the cost of flagging many who do not. The two most common reasons for a false failure in one ear are vernix and middle ear fluid, and both are harmless and temporary.

Vernix is the waxy coating that protects your baby’s skin in the womb. It can plug the ear canal and block the sound signals the screening equipment sends in. When researchers examined newborns who failed one-ear screening and then cleaned the ear canal, about three-quarters of those ears passed on a repeat test right away.³ Another study found that roughly 28 percent of tested ears had enough vernix to completely obscure the eardrum, and cleaning it raised pass rates substantially.⁴

Middle ear effusion, sometimes called fluid behind the eardrum, is the other big player. Babies can be born with residual amniotic fluid or develop mild inflammation in the middle ear space. In one study, fluid was found in about 65 percent of newborns who failed their hearing screen.⁵ The fluid usually clears on its own: a separate hospital cohort showed spontaneous clearance in about a quarter of affected babies, while just over a fifth eventually needed tiny ear tubes to drain persistent effusion.⁶ Either way, once the fluid is gone, hearing returns to normal in these babies.

Because of these transient causes, screening programs expect a high false-positive rate. One large screening study found that of newborns who completed follow-up after failing, nearly two-thirds turned out to have completely normal hearing.⁷ That does not mean the screening is flawed. It means the test is built to err on the side of catching every real problem, even if it worries a lot of parents whose babies hear perfectly well.

What the Screening Actually Measures

Hospitals typically use one of two screening technologies, and each picks up slightly different things. OAE screening measures faint sounds produced by the inner ear (the cochlea) in response to a click played through a tiny earphone. If something blocks the ear canal or the middle ear is full of fluid, the test will register a failure even if the inner ear is fine. That is why vernix and effusion cause so many false positives with OAE.

The other method, automated auditory brainstem response (AABR), goes a step further. It places sensors on the baby’s head and measures electrical activity along the hearing nerve up through the brainstem.⁸ Because it tests the nerve pathway itself, AABR can pick up a rare condition called auditory neuropathy, where the inner ear works but the signal does not travel properly to the brain. Many hospitals now use both tests, or at least use AABR as a follow-up when OAE fails.

If your baby failed in one ear, knowing which test was used helps set expectations. An OAE-only failure is more likely to be from ear canal debris or fluid. An AABR failure, especially a persistent one, warrants closer follow-up because it could signal a nerve-level issue.

What Follow-Up Looks Like

Guidelines recommend that all screening be completed by one month of age.⁹ If your baby does not pass the initial screen in one ear, most hospitals will retest before you go home or schedule a rescreen within a few weeks. If that retest still comes back as “refer,” the next step is a diagnostic evaluation with a pediatric audiologist.

Diagnostic testing is more detailed than screening. A full auditory brainstem response test done while the baby sleeps can measure hearing thresholds at specific frequencies, giving a much clearer picture of what the ear can and cannot detect. Tympanometry, which measures how the eardrum moves in response to air pressure, helps determine whether middle ear fluid is causing the problem.¹⁰ Together, these tests can distinguish between temporary conductive issues and permanent sensorineural loss.

The biggest risk at this stage is not the hearing loss itself but losing track of the follow-up. Studies consistently show that a meaningful number of families do not return for the recommended retest, and delayed diagnosis can cost a child months of early intervention time. If your baby fails in one ear, keeping that audiology appointment matters more than the initial screening result.

When the Hearing Loss Is Real

For a small percentage of babies, the one-ear failure reflects a genuine permanent hearing loss. The causes fall into a few broad categories.

Genetics accounts for the majority of congenital hearing loss in developed countries.¹¹ While genetic hearing loss is often bilateral, it can affect just one ear. Researchers studying children with unilateral sensorineural hearing loss found identifiable genetic variants in about one in five patients, most commonly involving a gene called GJB2 that plays a role in inner ear function.¹² Other genes linked to unilateral loss include TECTA and COCH.¹³

Congenital cytomegalovirus (CMV) infection is the most common non-genetic cause. CMV is a widespread virus that most adults carry without knowing it, but when a mother is infected or re-infected during pregnancy, the virus can damage the baby’s inner ear. CMV-related hearing loss is a particular concern because it can be progressive: a child may pass a hearing screen in one ear at birth and still develop hearing loss in that ear months or years later. In one study of children with CMV-associated hearing loss who initially failed the screen in only one ear, half went on to develop bilateral hearing loss over time.¹⁴ Among all children identified with CMV-related hearing loss in a multi-center study, about a quarter had unilateral loss at the time of initial detection.¹⁵

Babies who spent time in the neonatal intensive care unit face additional risks. Exposure to certain medications that can damage hearing, prolonged mechanical ventilation, very low birth weight, and prematurity all raise the odds of failing a hearing screen.¹⁶ Congenital structural abnormalities of the ear or associated syndromes were the single strongest predictor of screening failure in both NICU and well-baby nursery populations.

How Unilateral Hearing Loss Affects a Child’s Development

For decades, hearing loss in one ear was considered a minor issue. The assumption was that the other ear compensated well enough. Research over the past two decades has changed that view considerably.

Children with confirmed unilateral hearing loss tend to score lower on language and verbal tests compared with siblings who hear normally in both ears. They need individualized education plans at roughly three times the rate of their normally hearing peers and speech therapy at about twice the rate, and these difficulties do not simply disappear as the child ages.¹⁷ A systematic review of the topic found that most studies reported poorer scores on various speech and language tests, with the effects more pronounced when the hearing loss was severe to profound. A minority of studies found no significant differences, and a couple noted that early speech problems improved over time.¹⁸

The most consistent difficulty shows up in noisy environments. A child with one working ear has a much harder time understanding speech when there is background noise, and their ability to locate where sounds are coming from is dramatically reduced. In controlled testing, children with unilateral hearing loss correctly identified word sounds about 84 percent of the time in noise, compared to 90 percent for normally hearing peers. The gap for locating sounds was even wider: average localization errors were about 28 degrees for the affected group versus 6 degrees for children with normal hearing.¹⁹

The brain’s ability to process sounds from both ears also takes a hit. Losing input from one ear during development weakens the brain’s representation of that ear, and this can persist even if hearing is later restored on that side.²⁰ This is one reason audiologists now recommend earlier intervention rather than a wait-and-see approach.

Assistive Devices and Classroom Support

When a baby is confirmed to have permanent hearing loss in one ear, options exist even in infancy. Bone conduction hearing aids, which transmit sound vibrations through the skull to the working inner ear, can be fitted on a soft headband in babies as young as a few months old. A study of children under two found that bone conduction devices significantly improved auditory responses and development milestones.²¹ A systematic review concluded that trialing a bone conduction device on a headband is a reasonable first step for children with congenital unilateral deafness, since it carries no surgical risk and can be discontinued if it does not help.²²

For school-age children, FM systems (wireless microphones that send a teacher’s voice directly to a receiver in the child’s ear) can make a significant difference in the classroom. A review of academic outcomes in children with unilateral loss noted that assistive devices such as FM systems, hearing aids, and bone-anchored devices may all provide classroom benefits, and that early intervention tends to produce more favorable outcomes.²³ Preferential seating, where the child sits with their good ear toward the teacher, is a simple accommodation that helps in the meantime.

Managing Parental Anxiety After a Failed Screen

If your baby just failed a hearing test in one ear, you are probably feeling some combination of fear, confusion, and guilt. Research on parental reactions to a failed newborn screen confirms that this anxiety is almost universal but tends to drop sharply as the process moves forward. In one study, about three-quarters of mothers reported mild anxiety after the initial screening failure, and the proportion reporting severe anxiety fell by half before the second screening.²⁴ Another study that measured both state and trait anxiety in parents of babies who failed screening found that overall anxiety levels were low, suggesting that when the screening program communicates clearly, most families cope well.²⁵

The most helpful thing you can do is show up for the follow-up appointment. A failed screen is not a diagnosis. It is a reason to look more closely. Most babies who fail in one ear turn out to hear just fine once the ear canal clears or the fluid drains. And even when the hearing loss is real, the fact that it was caught this early puts your child in a far better position than the generations of children whose unilateral hearing loss went undetected until they struggled in school.

Why CMV Testing Deserves a Mention at the Follow-Up

If your baby’s one-ear failure turns out to be a genuine sensorineural hearing loss, it is worth asking the audiologist or pediatrician about congenital CMV testing. Expert guidelines now emphasize the connection between CMV and hearing loss, and early identification of the virus opens the door to antiviral treatment that may limit further hearing damage.²⁶ CMV testing is simple, usually requiring a urine or saliva sample, but it is most reliable when done within the first few weeks of life. After about three weeks, distinguishing a congenital infection from one acquired after birth becomes more difficult.

This matters because, as noted earlier, CMV-related hearing loss can worsen over time. A child who passes in one ear at birth may still lose hearing in that ear months or years later if CMV is the underlying cause.¹⁴ Knowing whether CMV is involved guides the monitoring plan: children with confirmed CMV-related hearing loss need regular audiological follow-up through early childhood, even on the side that currently tests normally. Not every hospital automatically runs this test after a failed screen, so parents may need to ask for it specifically.