Deafness that is present at birth is called congenital deafness. Most cases of congenital deafness have a genetic cause. In addition to hereditary genetics, the genes may mutate and cause a syndrome that causes congenital hearing loss or deafness. Congenital deafness is not as common as deafness that is acquired after birth due to noise exposure, illness, or due to age.

The frequency of congenital deafness is approximately one out of every one or two thousand births. Bilateral hearing loss is hearing loss affecting both ears. Unilateral hearing loss only affects one ear. Bilateral congenital hearing loss is more common than unilateral congenital hearing loss.

Congenital deafness can be caused by a heredity, genetic condition, or deformity of the ear. Genetic deafness through the normal heredity of genes is the most common cause of congenital deafness. The parents who are deaf or carry recessive genes that cause deafness have a high risk of having infants with genetic deafness. The deafness may have been passed down through numerous generations of the family.

Not all genetic hearing loss is inherited from the parents. Mutations of the genes can cause a syndrome that was not inherited from the parents. About twenty percent of congenital hearing loss is caused by syndromes caused by genetic mutations or gene abnormalities.

The genetic syndromes that can cause deafness are usually unexpected. Families of children born with these syndromes rarely have any other children with that syndrome in the family’s medical history. Many of these non-hereditary syndromes cause several birth defects including hearing loss or deafness. Usher syndrome, CHARGE syndrome, Mohr-Tranebjaerg syndrome, Jervell and Lange-Nielsen Syndrome, and Waardenburg syndrome are examples of syndromes that can cause congenital hearing loss.

Numerous hospitals across the world routinely test newborns for hearing loss. If the infant has not had a hearing screening or the test failed to detect a congenital hearing loss, a hearing loss may be suspected if the infant has a pattern of failing to react to auditory stimuli. Infants have a natural startle reflex which causes jerky movement in reaction to loud noise. The absence of the startle reflex can mean that the infant is not hearing noise that would otherwise cause the startle reflex.