Approximately 1 in 1,000 infants are born deaf due to genetic or environmental causes (e.g. prenatal infections).
Deafness may be isolated or sporadic, or may be just one component of  a more complex clinical profile involving various other disorders or syndromes. The most common genetic forms are bilateral and of the perceptive type. All frequencies can be affected and some hereditary forms present impairment regarding high, medium, and low tones.

Onset may occur at the time of birth or later in life and the evolution may be variable, progressive, or stationary. Profound or total deafness at birth impairs the child's ability to acquire spoken language.

Most forms of congenital deafness are hereditary, with recessive transmission, or of a sporadic nature.

In both cases it has been demonstrated that a single gene is responsible. This gene regulates the synthesis of a number of proteins - i.e. connexins, which are needed for the auditory system to function properly. In some centers, screening is performed, making it possible to conduct research on over 50 % of the mutations responsible for causing the most common forms congenital hearing impairment, whether sporadic or hereditary, but only those involving the GJB2 gene for connexin 26.

Being able to confirm a potential case of deafness even before the child is born can make it easier to arrange for the appropriate therapeutic program with specialists in the sector. They are then able to make decisions in the way of surgery, speech therapy, or prosthetic aids, in order to develop the audio-sensory capabilities needed to restore a functional level of hearing to the patient.