9Newborn & infant hearing screening

FWhy screen every newborn

Screening is justified when a condition is common enough, serious enough, detectable early, and treatable better early than late. Congenital hearing loss meets every criterion: at one to two per thousand births it is among the commonest conditions present at birth (Module 8); undetected, it derails language and development; it can be found painlessly in the newborn nursery; and — the decisive point — outcomes are dramatically better when treatment begins early. Relying on parents or doctors to notice deafness fails precisely because a deaf baby behaves normally in every other way.

FTThe evidence that timing matters

The foundational evidence is that children whose hearing loss is identified early — by around six months — achieve markedly better language than those identified later, largely independent of the degree of loss. That single finding transformed the field: it meant the date of detection was itself a powerful determinant of outcome, and it provided the rationale for moving from risk-based testing to universal newborn screening.[1998]

This dovetails exactly with Chapter 3: early identification matters because it allows input to reach the brain while the sensitive period is open. Screening is, in effect, the public-health instrument for acting on the science of plasticity.

FTThe 1–3–6 framework

Early hearing detection and intervention programmes are organised around a simple, memorable set of milestones — 1–3–6: screen by 1 month, confirm the diagnosis by 3 months, and begin intervention by 6 months. Each step has a deadline because each delay eats into the window. Step through the pathway below.

COAE and AABR

Two physiological tests do the screening, neither needing the baby's cooperation. Otoacoustic emissions (OAE) check that the cochlear amplifier — the outer hair cells (Chapter 2) — is working; they are quick and cheap but test only the cochlea. Automated auditory brainstem response (AABR) checks that the signal travels up the auditory nerve and brainstem. The distinction matters: AABR detects auditory neuropathy spectrum disorder, in which the cochlea works (OAE present) but neural transmission fails — a condition an OAE-only screen would miss. This is why programmes screening high-risk infants, especially from neonatal intensive care, rely on AABR.

FThe Indian coverage challenge

For India the obstacle is not the technology — OAE and AABR units are inexpensive and simple to use — but reach. A large share of births occur outside tertiary hospitals, in district facilities or at home, where no screening programme operates. Universal coverage therefore depends on embedding screening into routine maternal and child health servicesand the immunisation contacts that already reach most infants, and on the national deafness programme's push to extend screening beyond the big centres. Without that reach, screening protects only the minority born where it is offered.[2018]

CBeyond the birth test

A newborn screen is necessary but not sufficient. Some losses are delayed or progressive — congenital CMV is the classic example (Module 8) — so a child can pass at birth and still need help later. Effective programmes therefore add ongoing surveillance, attention to parental concern about speech, and a low threshold to re-test. The birth screen opens the door; vigilance keeps it open through the years that matter.

With the Indian story now complete — its scale, its causes, and the system that should catch it early — we widen the lens to the world: the global picture and its projection to 2050 (Module 10).