A newborn with kernicterus has very high levels of bilirubin in the bloodstream, which causes damage to the brain and spinal cord. In the US, newborns are routinely tested for the presence of too much bilirubin in the bloodstream.

Neonatal jaundice is a term used to describe higher than normal levels of bilirubin in a newborn. Kernicterus occurs when neonatal jaundice is severe.

Kernicterus can cause cerebral palsy, mental retardation, and hearing loss. In the US, there were less than 100 cases of kernicterus reported in the last 15 years.