Hearing Loss at Birth (Congenital Hearing Loss)
The term congenital hearing loss means the hearing loss is present at birth. Congenital hearing loss can be caused by genetic or nongenetic factors.
Nongenetic factors can account for about 25% of congenital hearing loss. Nongenetic factors that are known to cause congenital hearing loss include:
- Maternal infections, such as rubella (German measles), cytomegalovirus, or herpes simplex virus
- Low birth weight
- Birth injuries
- Toxins including drugs and alcohol consumed by the mother during pregnancy
- Complications associated with the Rh factor in the blood/jaundice
- Maternal diabetes
- Toxemia during pregnancy
- Lack of oxygen (anoxia)
Genetic factors (hereditary) are thought to cause more than 50% of all hearing loss. Hearing loss from genetic defects can be present at birth or develop later on in life. Most genetic hearing loss can be described as autosomal recessive or autosomal dominant. Other, more rare types of genetic hearing loss include X-linked (related to the sex chromosome) or mitochondrial inheritance patterns.
In autosomal recessive hearing loss, both parents carry the recessive gene and pass it along to the child. Parents are often surprised to discover their child has a hearing loss because they are not aware that they are carrying a defective gene. This type of inheritance pattern accounts for about 70% of all genetic hearing loss.
An autosomal dominant hearing loss occurs when an abnormal gene from one parent is able to cause hearing loss even though the matching gene from the other parent is normal. The parent who is carrying the dominant gene may also have hearing loss as well as other signs and symptoms that make up a genetic syndrome. The autosomal dominant pattern accounts for 15% of all genetic hearing loss cases.
Genetic syndromes have a group of signs and symptoms that together indicate a specific disease. There are many genetic syndromes that include hearing loss as one of the symptoms.
- Down syndrome
- Usher syndrome
- Treacher Collins syndrome
- Crouzon syndrome
- Alport syndrome
- Waardenburg syndrome