Nobody knows what causes autism. It seems to be at least partly genetic—identical twins are more likely to both be autistic than fraternal twins—but may also have some environmental factor. Researchers in Perth, Western Australia, asked whether obstetric complications and autism were linked.

What the researchers wanted to know: Is autism more likely in children whose mothers had obstetric complications around the time they were born?

What they did: The researchers collected information on children diagnosed with autism in Western Australia and linked them up with a database of every child born in the state since 1980. They identified 465 children with autism and compared them with 481 siblings and 1,313 randomly selected nonautistic children born in the same time (between 1980 and 1997, although 1996–1997 births were left out because autistic children born then might not have been diagnosed yet).

What they found: Kids with autism were more likely to have had obstetric problems during pregnancy, labor, delivery, and soon after birth than kids without autism. Autistic children were more likely to have threatened to miscarry early in the pregnancy; also, both mothers and fathers of autistic children were older than parents of children without autism. Siblings of autistic children had fewer perinatal complications than their autistic siblings but more than the children without autism.

What it means to you: This research lends support to the idea that autistic children are already different at the time they're born, instead of their condition being brought on by something that happens later.

Caveats: This probably doesn't mean that obstetric complications cause autism, the authors say, but both the obsetric problems and autism might be caused by some of the same genes.

Find out more: Autism information from the CDC: http://www.cdc.gov/

Read the article: Glasson, E.J. et al. "Perinatal Factors and the Development of Autism." Archives of General Psychiatry. June 2004, Vol. 61, pp. 618–627.

Abstract online: http://archpsyc.ama-assn.org/