Flu While Pregnant Increases Risk of Autism in Baby, Denmark Study Finds

Researchers in Denmark have found that pregnant women who get the flu were twice as likely to give birth to a child later diagnosed with autism, although the data suggests the risk is still quite low and not cause for alarm, Reuters health reported.

The research does lead doctors to more critically examine the effect of a pregnant woman’s health has on her unborn fetus and how treatment of any medical issues – such as flu – lowers the risk of children developing conditions later in life, such as autism.

In the U.S., about one in 88 children is now diagnosed with autism or a related disorder.

Researchers said it is possible changes in a mother's immune system could affect the unborn child’s developing brain. But the evidence is still not conclusive and much more research needs to be done before there is a medical consensus of cause and effect.

Researchers said it's possible that activation of a mother's immune system  such as by infection with the influenza virus – could affect a fetus's developing brain. But they urged caution with the new findings, especially because of statistical limitations in their number-crunching.

"I really want to emphasize that this is not something you should worry about," said lead author Dr. Hjordis Osk Atladottir, from the University of Aarhus in Denmark

"Ninety-nine percent of women with influenza do not have a child with autism," she told Reuters Health. "If it were me that was pregnant, I wouldn't do anything different from before, because our research is so early and exploratory."

The data came from a study of more than 100,000 pregnant Danish women between 1996 and 2002. The women’s progress through their pregnancies, including any illnesses, was chronicled during the study. The team found that 1 percent of all kids were diagnosed with autism, including 0.4 percent with infantile. Of the 808 women who claimed to have the flu while pregnant, seven of those babies, or 0.87 percent, were diagnosed with infantile autism, compared to the rate of 0.4 percent among kids in general.

There were also a small number of children with an increased risk to develop autism or infantile autism when their mothers had a fever lasting at least a week during pregnancy, as well as mothers who took antibiotics.

"It is highly recommended that women avoid infection during pregnancy, and there are a variety of very practical ways to decrease the likelihood of this," Paul Patterson, who studies the immune system and brain development at the California Institute of Technology in Pasadena, told Reuters Health.

The U.S. Centers for Disease Control and Prevention still recommends  women get a flu vaccine while pregnant because pregnant women are more likely to suffer from serious complications from the flu than the general population.