A new study from UC Davis researchers found that women who ran a fever during pregnancy had twice the risk of having a baby with autism. The study offered an easy fix, too: Women who controlled the fever with Tylenol or a similar fever-reducing medication eliminated the risk.

The findings mesh with other research linking diabetes and obesity during pregnancy to a higher risk of having a child with a developmental delay or autism. The two conditions - fever and diabetes - are associated with an inflammatory response in the body that researchers say may injure the developing brain.

Researchers from the UC Davis MIND Institute, which is dedicated to studying autism, say the latest findings build on discoveries about risks and protections faced by pregnant women in Northern California. Risks for having a child with autism also include living within a quarter-mile of a highway. Protections include taking prenatal vitamins before and during pregnancy.

"We're adding more pieces to the set of evidence to try to figure it all out," said Irva Hertz-Picciotto, a professor of public health at UC Davis and principal investigator of CHARGE, the Childhood Autism Risks from Genetics and the Environment study.

Hertz-Picciotto said the findings were based on questionnaires filled out by more than 1,100 mothers of typically developing children and those with children with developmental delays or autism.

The study did not show an elevated risk of having a child with autism if mothers had the flu. But a fever from any cause, such as a bacterial infection, during pregnancy was twice as likely to be described by mothers with children with autism and 2.5 times more likely in mothers of children with developmental delays.

Mothers who took anti-fever medication had the same risk of having a child with autism as mothers who reported no fever, the study found.

The fever study raises the question of whether chemicals the body releases to fight infection, called cytokines, may pass through the placenta and have a damaging effect on the fetus, said Ousseny Zerbo, lead author of the study, who was a doctoral candidate with UC Davis when the study was conducted.

Zerbo said cytokines are produced during acute inflammation that occurs when someone has a fever. The chemicals are also produced steadily in people with diabetes, who have a 2.3 times higher risk of having a child with developmental delays.

The findings are similar in magnitude to a phase of the CHARGE study that examined women who lived near a highway when pregnant. The study found that women who reported living within 1,000 feet of a major freeway during the third trimester of pregnancy were 2.2 times more likely to have a child with autism.

Results of the CHARGE study have also concluded that women who took a prenatal vitamin before and during pregnancy reduced their risk of having a child with autism. Those who skipped vitamins saw a 60 percent higher chance of having a child with the condition.

Hertz-Picciotto said it's possible that women who take the vitamins and encounter none of the risks will still have a child with a developmental delay or autism. She said genes play a major role. And more studies need to be completed to confirm her team's findings and examine other genetic and environmental triggers.

"That's why we're continuing to cast a wide net, and hopefully it will begin to fall into place," she said.

The fever study was published online in the Journal of Autism and Developmental Disorders.

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