What exactly causes autism is still uncertain, but researchers are investigating the possibility that a mother having the flu while she is pregnant may increase the likelihood of her child being born with the condition.

Danish scientists and the U.S. Centers for Disease Control and Prevention looked at about 97,000 children ages 8 to 14 who were born in Denmark between 1997 and 2003—of which one percent had been diagnosed with autism—and their mothers. They found that mothers who had the flu while pregnant were twice as likely to give birth to a child on the autism spectrum. If their fever had lasted more than a week and it was before the third trimester, they were three times as likely.

The study is based largely on what the mothers reported, rather than a medical diagnosis of the flu, so the researchers caution about reading too much into their findings at this point.

The Center for Disease Control already recommends that all pregnant women get a flu shot.

[Yahoo!]