In a study that's already being greeted with notes of caution, Danish researchers report that children whose mothers had the flu or ran a fever lasting more than a week during pregnancy had an increased risk of developing an autism spectrum disorder.
U.S. health officials stress that the new study, out in today's Pediatrics, is "exploratory" and does not offer a specific cause of the developmental disability.
The study analyzed data collected from 97,000 mothers of children born from 1997 through 2003. It found no association between mothers who reported common respiratory or sinus infections, common colds, urinary tract or genital infections, during pregnancy and autism in their offspring.
But children whose mothers reported influenza during pregnancy had twice the risk of being diagnosed with autism before age 3, and children whose mothers had a fever for more than seven days had a threefold risk.
There was also a small increased risk of autism after the mother's use of various antibiotics during pregnancy. The study did not specify the conditions for which the antibiotics were prescribed.
"The study is really exploratory, and more research needs to be done to understand how maternal infections, as well as other risk factors, influence the risk of autism spectrum disorders," says Coleen Boyle, director of the Centers for Disease Control and Prevention's National Center on Birth Defects and Developmental Disabilities. "We need to have more information to get a better sense of what's going on here."