The 1-3-6 Rule: Newborn Hearing Screening and Red Flags

The 1-3-6 rule is the benchmark for newborn hearing screening: every baby is screened by 1 month of age, any hearing loss is confirmed by 3 months, and intervention begins by 6 months. Where universal screening is not yet possible, high-risk babies must be screened, and every doctor who sees young children should know the milestones and red flags that point to hearing loss.

That is the practical message of Dr. Dilpreet Bajwa, Sr. Consultant, ENT, ENT Surgery, Artemis Hospitals, Gurugram, India. In her experience most children with hearing loss reach a specialist late, often after the age of 2, when the critical period for language development is almost over. The delay is a failure of detection, and much of it can be fixed by primary care doctors, paediatricians and parents who know what to look for.

This article covers the detection side of the pathway. The complete guide to cochlear implants in children gives the overview, and the article on cochlear implant candidacy, timing, surgery and rehabilitation covers what happens once a severe loss is confirmed.

How we hear: conductive, sensorineural and mixed hearing loss

Hearing loss is classified as conductive, sensorineural or mixed according to where in the ear the problem lies. The ear has three working sections. The pinna, the visible outer ear, leads into the external auditory canal, about 2.5 cm long, which ends at the tympanic membrane (eardrum). Behind the eardrum sit the three auditory ossicles, the bones of hearing; the third, the stapes, connects to the cochlea of the inner ear. From the cochlea, the auditory nerve carries signals to the brain.

When sound waves strike the eardrum, it vibrates and sets the ossicles moving. Their movement makes the fluid inside the cochlea vibrate, which stimulates frequency-specific hair cells, and those hair cells in turn stimulate the nerve.

Where the problem lies determines the type of hearing loss:

• Conductive hearing loss arises in the outer or middle ear: a malformed pinna, a narrowed (stenosed) canal, wax or debris, a perforated eardrum or infection.
• Sensorineural hearing loss arises in the cochlea or the nerve.
• Mixed hearing loss combines the two.

The distinction matters because it predicts treatment. Conductive loss is often temporary and treatable: wax and debris can be cleared, and fluid behind the eardrum is treated until it dries up. Mixed and purely sensorineural loss usually does not respond to medication, and the patient is likely to need a hearing aid or a cochlear implant.

How to read an audiogram: decibels, frequency and degrees of hearing loss

An audiogram shows how loud a sound must be, in decibels, before a person hears it at each frequency, and the result places the hearing loss on a scale from normal to profound. Sound is the transmission of energy from one air particle to the next. Two of its qualities matter clinically. Intensity, the loudness of a sound, is measured in decibels (dB). Frequency, its pitch, is measured in hertz (Hz). Female voices tend to be higher in frequency and male voices lower, though every voice combines many frequencies.

The chart plots the softest sound a person can hear (in decibels) against frequency. The two axes are needed because hearing is rarely uniform: a person may hear 20 dB at one frequency but miss 2,000 Hz at the same level.

The most important feature on the chart is the "speech banana", the shaded, banana-shaped zone where most speech sounds fall. Dr. Bajwa uses it to explain why even a modest loss matters. A loss of about 40 dB causes a child to miss the soft, high-frequency consonant sounds of speech, and 40 dB is not a large loss. A loss of 60 dB can mean missing an entire conversation.

The scale Dr. Bajwa teaches is:

For context, a soft whisper is about 30 dB, normal conversation sits between 40 and 60 dB, and an aeroplane passing overhead is about 120 dB. Because ordinary speech falls in the 40 to 60 dB range, even a child with mild hearing loss struggles to follow normal conversation.

Newborn hearing screening: why it matters at birth

Newborn hearing screening matters because a child whose hearing loss is missed at birth is likely to stay undiagnosed for the first two years of life and to return after the age of 2, when the critical period for language development is almost over. Screening is routine at birth in developed countries. In India, Dr. Bajwa notes, most corporate hospitals now screen newborns, but government facilities largely do not.

The 1-3-6 rule: screen by 1 month, diagnose by 3, intervene by 6

The standard followed in developed countries has three deadlines:

1. Screen by 1 month. Every baby has a screening test at or before 1 month of age.
2. Diagnose by 3 months. A baby who does not pass screening has the hearing loss confirmed by 3 months.
3. Intervene by 6 months. Appropriate intervention starts by 6 months: fitting a hearing aid, registering the child for rehabilitation, tracking progress with the hearing aid, or planning a cochlear implant if the child needs one.

Dr. Bajwa acknowledges that this is the ideal rather than the norm in many health systems. Her minimum standard is that high-risk babies are always screened.

Which babies are at high risk of hearing loss

The babies Dr. Bajwa would always screen are those who:

• needed a stay in the neonatal intensive care unit (NICU);
• were born prematurely;
• had birth asphyxia, seizures or severe jaundice after birth, high enough to need an exchange transfusion;
• had meningitis or a viral infection;
• were exposed to ototoxic drugs, medicines that can damage the inner ear;
• were exposed to cytomegalovirus (CMV), for example through maternal CMV infection;
• appear syndromic, with features that suggest a genetic syndrome.

The OAE test: otoacoustic emissions screening for newborns

The first-line newborn hearing screening test is otoacoustic emissions (OAE). A healthy cochlea does not only receive sound; its outer hair cells also emit faint sound waves of their own, and a small probe in the ear canal picks these up. A present OAE response means the child probably does not have significant hearing loss. An absent response means the child must be rechecked, or examined for an ear infection that needs treatment, and the test repeated. For babies who spent more than five days in neonatal intensive care, the Joint Committee on Infant Hearing recommends automated auditory brainstem response (ABR) screening, because OAE alone cannot detect auditory neuropathy.

Dr. Bajwa highlights why OAE suits screening at scale. It is non-invasive and painless, takes from a few seconds to a minute, and runs on a small portable device that can be carried to wherever the mother and baby are admitted.

Only when OAE suggests a hearing loss does the child move to the full test battery.

Diagnostic hearing tests: BERA, ASSR and behavioural audiometry

When screening suggests a hearing loss, the diagnosis is confirmed with a battery of tests. The full battery includes:

• Brainstem evoked response audiometry (BERA), also called auditory brainstem response (ABR) testing, which records the nerve and brainstem response to sound.
• Auditory steady-state response (ASSR), a related electrophysiological test that estimates hearing levels across frequencies.
• Behavioural audiometry, including visual reinforcement audiometry (VRA) and conditioned play audiometry.

In visual reinforcement and conditioned play audiometry, the child is trained to respond to each sound, for example by placing a block in a bin whenever a tone is heard. Dr. Bajwa regards their results as more precise and more useful than the electrophysiological tests. The drawback is time: conditioning a small child takes repeated visits, which working parents often cannot manage. BERA and ASSR are the quicker alternative for establishing whether a child has hearing loss.

Hearing and speech milestones from birth to 12 months

Where there is no OAE machine, no BERA and no audiologist, the clinician's knowledge of normal milestones becomes the screening tool. Dr. Bajwa recommends a milestone chart from the Indiana Department of Health and believes every paediatrician and general practitioner should keep one in the consulting room to share with parents. The milestones she highlights:

• Birth to 3 months: general awareness of sound. The baby stops suckling when spoken to, startles or blinks at a loud noise, and the eyes widen.
• 3 to 6 months: the baby looks with the eyes towards where a sound is coming from, and begins to babble ("mama", "gaga"). At this age "mama" is a sound the child can make, not a call for the mother.
• 6 to 9 months: the baby responds to small, familiar words such as "no" and "bye".
• By 12 months: the child responds to his or her own name.

Signs of hearing loss in babies: red flags for referral

The red flags that should prompt testing, or at least a referral for examination by an ENT surgeon, are:

• no startle or blink to loud sounds at any age, including in a newborn;
• no babbling by 6 months;
• not a single word by 12 months;
• not turning to his or her name;
• heavy reliance on visual cues.

The last point is easy to miss. Parents often report that the child responds only when they face him or her. Such a child is reading facial expressions and lip movements rather than hearing.

Older children and progressive loss

Not all hearing loss is present at birth. A child may be born with a mild to moderate loss that progresses over several years, and children do not report it themselves. The signs are a child who seems inattentive in class or who repeatedly asks "what?". A regression in speech, where a child who used to talk falls silent or loses words, failing developmental milestones, or a syndromic appearance all call for urgent referral.

When parents raise the concern

The most important red flag of all, in Dr. Bajwa's view, is a parent who says the child may not be hearing. Parents rarely say this, because most either do not know the signs or are in denial. When they do, the wrong response is reassurance that the child will talk in his or her own time. That child must be referred for testing, or at least for an ENT examination.

What the ENT assessment of a child looks for

The ENT evaluation begins the moment the child walks in. Facial appearance can give the first clue: a child with Down syndrome, for example, can have both a conductive and a sensorineural component to the hearing loss. Adenoid facies, the open-mouthed appearance of a child with enlarged adenoids, matters because adenoid enlargement is very common and causes middle ear effusion, fluid behind the eardrum. Many children present with a temporary hearing loss from middle ear effusion and recover fully once it is treated.

The examination then establishes the state of the ear canal and eardrum. Wax, debris or discharge is cleared, the eardrum is checked for whether it is intact, and treatment follows accordingly. Once these treatable conductive causes are excluded, a child with a confirmed severe or profound sensorineural loss moves on to the questions covered in the cochlear implant candidacy and timing article: hearing aid or implant, and how soon.

Questions on adult hearing loss, chronic illness and follow-up care raised during the session are answered in the Live Discussion. Where a hearing aid is the right first step, the hearing aid fitting cost page sets out typical packages.