Mothers who had fevers during their pregnancies were more than twice as likely to have children with autism or developmental delays compared to mothers of normally developing children, according to a new study.

However researchers found that taking medications to control fevers while pregnant may be effective in decreasing the risk of giving birth to a child with autism or other abnormal neurodevelopmental disorders.

"Our study provides strong evidence that controlling fevers while pregnant may be effective in modifying the risk of having a child with autism or developmental delay," lead researcher Ousseny Zerbo from UC Davis said in a statement. "We recommend that pregnant women who develop fever take anti-pyretic medications and seek medical attention if their fever persists."

While previous studies have linked maternal infections like congenital rubella, measles, mumps and influenza during pregnancy to developmental disorders like autism and schizophrenia, the latest study, published in the Journal of Autism and Developmental Disorders, is believed to be the first to link fever from any cause, including flu, and its treatment during pregnancy to developmental delays in children.

The research, which was based on data from the Childhood Autism Risk from Genetics and the Environment (CHARGE) Study, included 538 children with autism, 163 children with developmental delay but not autism, and 421 typically developing children whose mothers completed surveys about whether they had the flu and/or fever during pregnancy and if they took medications to treat their ailments.

While flu during pregnancy was not associated with greater risk of having a child with autism or other developmental delays, fever from any cause during pregnancy was reported 2.12 times more by mothers of children with autism and 2.5 times more in mothers of children with other developmental delays, compared with mothers of children who developed normally.

However, the autism risk in children of mothers who took fever medication was not higher than the risk in children whose mothers reported no fever.

Previous studies also revealed that mothers who were obese or diabetic had a higher likelihood of having children with autism.

Professor Irva Hertz-Picciotto, principal investigator of CHARGE, explained that fever is caused by acute inflammation, which is the short-term, natural immune system reaction to infection or injury.  That chronic inflammation, which can damage healthy tissue, may be present in mothers with metabolic abnormalities like diabetes and obesity.

"Since an inflammatory state in the body accompanies obesity and diabetes as well as fever, the natural question is: Could inflammatory factors play a role in autism?" said Hertz-Picciotto.

Hertz-Picciotto explained that when a person contracts a bacterial or virus infection, their body generally reacts by mounting a healing response that involves the release of pro-inflammatory signaling molecules called cytokines from white blood cells into the bloodstream. 

Some of the signaling molecules released may penetrate the placental and reach the fetal central system, and can potentially alter levels of neurotransmitters and brain development if they reach the fetal central nervous system.