A new study in the journal Pediatrics has found that complications during childbirth, including low oxygen during delivery, can put children at greater risk of developing autism spectrum disorders.
Researchers from Harvard and Brown universities analysed data from 64 studies, finding that birth injuries, low birth weight, low blood iron and being born in the summer all increase the risk.
Many of these restrict blood flow to the brain, which can combine with genetic factors to make it more likely that somebody will develop autism.
The study comes shortly after researchers at the University of Cambridge found that siblings of people with autism show a similar pattern of brain activity when looking at emotional facial expressions.
"Innovative research like this improves our fundamental understanding of how autism is passed through generations affecting some and not others," said Professor Chris Kennard, chairman of the Medical Research Council funding board for the study.
Find out about Barchester's support for adults and children with a wide range of Autistic spectrum conditions.