Autism may begin in the womb.

This theory may offer some relief to parents who believe vaccines are the cause of autism.

The new science suggests that an overgrowth of brain cells in early embryonic development is responsible for the symptoms of autism.

“In autism something is going terribly wrong with mechanisms that control the number of neurons beginning in prenatal life and may extend to perinatal and early post-natal life,” says lead author Eric Courchesne, Ph.D. When there are too many brain cells, the brain can’t wire itself up correctly. If there’s too much wiring in the prefrontal cortex, it could help explain why children with autism have poor social skills, difficulty communicating and why some may never learn to speak at all.