Since cerebral palsy refers to a group of disorders, there is no exact known cause. Some major causes are asphyxia, hypoxia of the brain, birth trauma or premature birth, genetic susceptibility, certain infections in the mother during and before birth, central nervous system infections, trauma, and consecutive hematomas. In most people with CP, the cause is unknown. After birth, the condition may be caused by toxins, physical brain injury, incidents involving hypoxia to the brain (such as drowning), and encephalitis or meningitis. Despite all of these causes, the cause of many individual cases of cerebral palsy is unknown.
Recent research has demonstrated that asphyxia is not the most important cause as it was once considered to be, though it still plays a role, probably accounting for about 10 percent of all cases. The research has shown that infections in the mother, even infections that are not easily detected, may triple the risk of the child developing the disorder.
Premature babies have a higher risk because their organs are not yet fully developed. This increases the risk of asphyxia and other injury to the brain, which in turn increases the incidence of cerebral palsy.
Also, some structural brain anomalies such as lissencephaly cause symptoms of CP, although whether that could be considered CP is a matter of opinion (some people say CP must be due to brain damage, whereas these people never had a normal brain). Often this goes along with rare chromosome disorders.