Deafness at birth—called congenital deafness —usually comes from a mix of genetic factors and problems during pregnancy or delivery , not from one single cause.

Quick Scoop

Around half of babies born deaf have a genetic cause , and the other half have non‑genetic causes such as infections, birth complications, or exposure to certain drugs or toxins before birth.

Main genetic causes

Genes are the most common reason for deafness at birth, especially in high‑income countries.

  • Non‑syndromic genetic deafness
    • Hearing loss is the only noticeable problem; no other major health issues.
* Often inherited in a **recessive pattern** , meaning both parents carry a gene variant even if they hear normally.
  • Syndromic genetic deafness
    • Deafness is part of a broader genetic syndrome, such as:
      • Usher syndrome (hearing loss plus progressive vision loss).
  * **Waardenburg syndrome** (hearing loss plus unusual hair, skin, or eye color).

  * **Down syndrome** (extra chromosome 21; higher risk of hearing problems).

Infections during pregnancy

Certain infections can damage the baby’s inner ear or auditory nerve while still in the womb.

Common culprits include:

  • Cytomegalovirus (CMV) – one of the leading non‑genetic causes of congenital deafness.
  • Rubella (German measles) – can damage the ears, eyes, and heart.
  • Toxoplasmosis, syphilis, and herpes simplex virus (HSV) – all linked to inner‑ear damage and hearing loss.

Birth‑related and medical factors

Problems around the time of birth can also lead to deafness.

  • Prematurity and low birth weight – very premature babies are more vulnerable to infections and other complications that affect hearing.
  • Lack of oxygen (hypoxia) or severe jaundice – can injure the auditory system.
  • Certain medications used in pregnancy or in the newborn period (such as some antibiotics or chemotherapy‑like drugs) may be ototoxic (harmful to the ear).

Environmental and structural causes

Sometimes the ear itself doesn’t form properly, or something in the environment interferes with development.

  • Malformations of the inner ear or auditory nerve – the structures simply don’t develop correctly.
  • Exposure to loud noise or toxins in pregnancy (rare but possible).

What this means for families

  • Many children born deaf have no obvious family history , because recessive gene variants can “hide” for generations.
  • Newborn hearing screening in the first days of life helps catch deafness early, which greatly improves language and development outcomes.

If you’d like, I can follow up with a simple table comparing genetic vs. non‑genetic causes of deafness at birth in a clear HTML‑style layout.