What percent of autistic children are born with autism and what develop it later?

It is estimated that about 1 in 100 children are born with autism spectrum disorder (ASD). The other 99% develop ASD later in life. The exact cause of ASD is unknown, but it is thought to be caused by a combination of genetic and environmental factors.

Genetic factors are thought to play a significant role in ASD, as the condition tends to run in families. However, not all children who have a family history of ASD will develop the condition.

Environmental factors that are thought to contribute to ASD include certain infections during pregnancy, such as rubella, exposure to certain chemicals, such as mercury, and prematurity.

It is important to note that there is no single cause of ASD. The condition is likely caused by a complex interaction of genetic and environmental factors.