Hearing in newborns and infants

By Shannon O’Leary, Audiologist

by Media Xpose

Childhood hearing loss, even when mild or unilateral (i.e., only in one ear), can result in significant delays in a child’s speech and language development, as well as their cognitive, social, and emotional development.

In turn, these delays can significantly affect literacy development, academic development and ultimately reduce a child’s ability to meet their maximum potential in life. Hearing loss can be from birth or can be acquired at a later stage in childhood. It is therefore critical that a child’s hearing be screened as early as possible (preferably at birth), but then monitored and checked regularly throughout childhood to ensure that any hearing loss that may be present is detected and appropriately managed at the earliest possible age.  

Developmental stages of hearing

A baby’s hearing is fully developed at birth. In fact, the human cochlea has normal adult function after the 20th week of gestation. A full-term newborn baby has therefore already been hearing sounds for at least four months.

They are also able to recognize their mother’s voice and studies have shown that newborns generally show a preference for their mother’s voice. In typically-developing hearing infants, we expect to see the following speech and hearing milestones between birth and 2 years of age:

Birth to 5 months

  • Reacts to loud sounds with startle reflex.
  • Is soothed and quieted by soft sounds.
  • Turns head toward a sound source.
  • Watches your face when you speak.
  • Smiles and makes noises when spoken to.
  • Seems to know certain voices and quiets down if crying.
  • Vocalises pleasure and displeasure sounds (e.g., laughs, giggles, coos, cries, fusses)

4 – 6 months

  • Looks or turns to new sounds.
  • Understands “no-no” and changes in tone of voice.
  • Enjoys rattles and other toys that make sounds.
  • Begins to repeat sounds / babble (e.g., “ooh”, “aah”, “ba-ba”).
  • Gets scared by a loud noise or voice.

7 – 12 months

  • Responds to his/her own name and familiar voices and environmental sounds (e.g., phone ringing).
  • Knows words for common things (e.g., “cup”, “shoe”) and sayings (e.g., “bye-bye”).
  • Makes babbling sounds, even when alone.
  • Starts to respond to requests (e.g., “come here”).
  • Looks at things or pictures when someone talks about them.
  • Enjoys turn-taking games such as peek-a-boo.
  • Imitates simple words and sounds; may use a few single words meaningfully.
  • Tries to communicate by actions or gestures.
  • Tries to repeat your sounds.
  • Attempts to imitate familiar sounds.

1 to 2 years

  • Follows 1-step commands when shown by a gesture.
  • Uses words he/she has learned often.
  • Uses 2- to 3-word sentences to talk and ask for things.
  • Says more words as each month passes.
  • Points to some body parts when asked.
  • Understands simple “yes-no” questions (e.g., “Are you hungry?”).
  • Understands simple phrases (e.g., “in the cup”, “on the table”).
  • Enjoys being read to.
  • Understands “not now” and “no more”.
  • Follows 2-step commands (e.g., “get your shoes”, “come here”).
  • Understands many action words (e.g., “run”, “jump”).

Screening for infant hearing

A child’s hearing can be evaluated from 24 hours of age. Many hospitals have a newborn hearing screening programme and parents are given the option of having a screening test performed on their child while still in hospital.

Hearing screening is quick, easy, non-invasive, and usually done while the baby is sleeping. A baby’s hearing can be screened during Otoacoustic Emissions (OAE) or Automated Auditory Brainstem Response (AABR); or both.

If the hospital does not have a newborn hearing screening programme, it is recommended that all babies should have a hearing screening before they are one month old.

OAE screening test: An OAE screening test measures the functioning of the outer hair cells of the cochlea. A small earbud is placed in the ear canal while the child sleeps. The machine emits a clicking sound into the ear canal and microphones which are situated in the earbud measures whether an otoacoustic emission (a little “bounce back” of the sound from the inner ear) can be measured in the ear canal.

AABR testing: This testing, sometimes also referred to as auditory evoked potential (AEP) testing, measures how the child’s inner ear and brain pathways for hearing are working. Electrodes are placed on the baby’s head and small earphones, or cups are placed over the ears.

Babies who do not pass the newborn hearing screening usually have a follow-up appointment where the screening is repeated while the babies are still in hospital or very soon thereafter.

Babies who do not pass the hearing screening at the follow-up appointment are then referred to an audiologist who specializes in paediatric diagnostic audiology assessments. Various tests are then used to establish whether the child has a hearing loss and if so, what type of hearing loss it is and how severe it is.

Test your infant

Older infants can be tested at any age by audiologists, using a variety of test techniques such as behavioural observational audiometry, Visual Reinforcement Audiometry (VRA) and Conditioned Play Audiometry. Even if your child has been tested at birth, it is important to test your infant if:

  • you have concerns about his/hearing
  • your child complains of pain in the ear
  • you observe discharge from the ear
  • your child does not seem to understand what you are saying to them
  • your child’s speech and language development is delayed

According to the World Health Organisation, over 60% of childhood hearing loss is treatable. This is due to causes such as impacted ear wax, infections, and pathologies of the middle ear (such otitis media with effusion or “glue ear”, where fluid collects in your child’s middle ear).

Conductive hearing loss is the most common type of childhood hearing loss and is usually caused by

  • impacted wax
  • infections of the external and/or middle ear
  • upper respiratory tract infections/congestions
  • allergies

The South African Association of Audiologists is a great platform to find an audiologist in your area. Visit www.saaudiology.co.za

Shannon O’Leary is an audiologist and owner of HearInAfrica. She is a graduate of the University of Cape Town, with a BSc in Logopaedics (1999) and a MSc in Speech & Language Pathology (2002).

She has a special interest in community-based audiology and has worked in a variety of private and public clinical settings, ranging from urban and rural clinics in South Africa, Africa and abroad.

T          +27 21 224 0018

E          hello@hearinafrica.com

W         www.hearinafrica.com 

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