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What is Congenital Hearing Loss?
Congenital hearing loss is the hearing loss that you’re born with. It might be due to a hereditary condition, birth infection, or pregnancy complication. Congenital hearing loss is one of the most common chronic conditions in children.
If you’ve had a baby In New Zealand, your child will most likely be offered a newborn hearing screening within a few days of birth. Usually, it’s done before Mum and baby go home from the hospital, but screening can be completed within three months of birth. The hearing screening is available at various local DHB Newborn Hearing Screeners or your hospital outpatient clinic.
The hearing screening technology is designed to pick up moderate to profound hearing loss and won’t necessarily pick up mild hearing loss.
The screening program helps children benefit from early intervention to support their speech, language and social development. When hearing impairment is detected early, the outcomes for your child’s education and confidence in social situations can be significantly improved.
What Causes Congenital Hearing Loss?
Most hearing impairments in children are genetic in origin and are usually a single gene defect. Other causes include environmental or prenatal factors.
The World Health Organisation indicates that 40% of congenital hearing loss is due to non-preventable genetic factors.
The other causes of hearing loss in babies include:
- certain infections the mother had during pregnancy, such as cytomegalovirus (in the herpes virus family), rubella, syphilis and meningitis (especially H influenza B)
- inappropriate use of certain medications during pregnancy, including aminoglycosides, cytotoxic drugs, antimalarial drugs, and diuretics
- birth asphyxia or lack of oxygen during birth
- low birth weight
- severe neonatal jaundice
- non-genetic malformations of the ear and the auditory nerve.
Although many causes of congenital hearing loss are known, a definitive cause is not identified in a substantial proportion of infants with hearing loss.
How Often Is Hearing Loss Present at Birth?
Neonatal screening for hearing loss is available for all babies in most developed countries. The generally accepted target is to screen newborns within one month of birth.
According to the Ministry of Health, in New Zealand, newborn hearing screening detects significant hearing loss in 135-170 babies per year, representing an incidence of about 3 per 1,000 births.
North America, Europe, and most developed countries have an estimated prevalence of congenital hearing loss of 1.33 per 1,000 births.
In developing countries in sub-Saharan Africa and South Asia, the prevalence increases to 24 per 1,000 births.
The presence or absence of risk factors for permanent congenital hearing loss plays a significant role in determining its prevalence.
Only 1.43% of children with hearing loss have a positive family history of congenital hearing loss. Having your baby screened is, therefore, rather important.
Babies and young children may also experience progressive hearing loss. Hence, it’s necessary to have a hearing screening at regular intervals, particularly for infants considered more at risk of developing hearing loss.
What Are the Risk Factors?
Risk factors for congenital hearing loss include:
- a family history of permanent congenital hearing loss
- the age of the mother
- gestational age
- low birth weight
- certain types of infection your baby may contract
- certain types of infection you experienced during pregnancy
- drug and alcohol use while pregnant
- if your baby has had assisted ventilation, venous access and aminoglycoside use while in a neonatal intensive care unit
You can’t prevent genetic risk factors for hearing loss in newborns. However, some risk factors, including infections and premature birth, can be lessened by education, medical services and prenatal support.
Some things you can do to lower the risk of congenital hearing loss for your baby include:
- talk to your doctor before pregnancy and ask for a preconception checkup
- make sure your vaccinations are up-to-date before becoming pregnant
- get checked for sexually transmitted infections
- protect yourself from diseases by practising good hygiene, safe sex and avoiding risky foods like undercooked meats.
How Is Hearing Loss in Babies Diagnosed and Treated?
Hearing screening and diagnosis within a few days of birth is ideal, as treatment may begin immediately.
Considerably improved outcomes for language development are associated with early identification of hearing loss and early intervention. The suggested timeframe for early intervention is before six months of age.
In 2007 the Universal Newborn Hearing Screening Programme (UNHSEIP) was introduced in New Zealand.
UNHSEIP has three core goals, called the ‘1-3-6‘ goals:
1. Babies are to be screened by one month of age.
3. Audiology assessment completed by three months of age.
6. Starting appropriate medical and audiological services and early intervention education services by six months of age.
The hearing loss test for your baby is a two-stage Automated Auditory Brainstem Response (aABR) screening test. This test connects electrodes to babies’ foreheads, and a computer checks how babies’ brain and auditory nerves respond to sound.
If a hearing loss is observed in the first test, a second aABR test will confirm if a hearing loss may be present. If a hearing loss is detected in the second test baby will be referred to an audiologist for full diagnostic testing.
The audiologist will perform various diagnostic tests to measure your baby’s responses to low, middle and high-pitched sounds. The audiologist will inform you about the services and support available to your family.