Prevalence is best calculated around the school entry age of about six years. In the industrialized world, the incidence is about 2 per 1000 live births. In the United States, the rate is thought to vary from between 1.5 to 4 per 1000 live births. This amounts to approximately 5,000-10,000 babies born with cerebral palsy each year in the United States. Each year, around 1,500 preschoolers are diagnosed with the disorder in the USA. In approximately 70 percent of all cases, cerebral palsy is found with some other disorder, the most common being mental retardation. Other disorders paired with CP include disorders of hearing, eyesight, epilepsy, perception of obstacles (such as judging how far away things are when driving a car), speech difficulties, and eating and drinking difficulties.
Overall, advances in care of pregnant mothers and their babies has not resulted in a noticeable decrease in cerebral palsy. Only the introduction of quality medical care to locations with less than adequate medical care has shown any decreases. The incidence increases with premature or very low-weight babies regardless of the quality of care. Twins are also four times more likely to develop cerebral palsy than single births, and triplets are more likely still to develop it.
Despite medical advances, the incidence and severity of cerebral palsy has actually increased over time. This may be attributed to medical advances in areas related to premature babies (which results in a greater survival rate) or the increased usage of artificial fertilization techniques.