Can flu during pregnancy cause autism?

Danish study says risk of autism may increase

If a mother has an infection or the flu during pregnancy, can it raise the risk of autism for her child? A new study out of Denmark suggests that the answer is "probably not" and "maybe" and that the issue definitely needs more study.

"Overall, we found little evidence that various types of mild common infectious diseases or febrile episodes during pregnancy were associated with ASD/infantile autism (autism spectrum disorders)," the study authors wrote.

But they also say their data suggest there are three scenarios in which there might be an increased risk of the child developing autism. If the mother had the flu, there was "a two-fold increased risk of infantile autism; if the mom had "prolonged episodes of fever" (lasting a week or more), the risk goes up threefold; "and use of various antibiotics during pregnancy were potential risk factors for ASD/infantile autism."

But the study authors also concede that the results may be skewed by multiple testing, contributing to the potential for "chance findings."

The study

These results of this study -- published Monday in Pediatrics, the journal of the American Academy of Pediatrics -- are based on researchers interviewing the mothers of 96,736 children born in Denmark between 1997 and 2003.

These women were asked nearly 200 questions in phone interviews around the 17th week of pregnancy, the 32nd week of pregnancy and six months after giving birth, long before any child could have been diagnosed with autism. This aimed to eliminate "recall bias," which can occur in studies where subjects self-report on their health. These women were asked whether they had any infections or episodes of fever and for how long, and whether they had taken any antibiotics.

The results

Among the over 96,000 children born, 976 were later diagnosed with autism spectrum disorders. The main signs and symptoms of autism involve difficulties with communication, social interactions and repetitive behaviors. According to the latest statistics from the U.S. Centers for Disease Control and Prevention, one in 88 children currently is diagnosed with autism, including one in 54 boys.

The study authors themselves note that a recently published Swedish study, which used inpatient hospital register data, "found no association between any prenatal infection and ASD."

The takeaway

"An important message is that even though we find an increased risk of ASD after influenza and prolonged periods of fever during pregnancy, the study is still speculative," lead study author Dr. Hjördis Osk Atladottir said in an e-mail. "It is important to bear in mind that when you look at the absolute numbers, we see that around 99 percent of women reporting to have had influenza or fever during pregnancy do not have children with ASD. We do not want pregnant women to worry. Our results are truly explorative."

She and her co-authors strongly recommend further research in this area.

In the meantime, Dr. Max Wiznitzer, a child neurologist at Rainbow Babies & Children's Hospital in Cleveland, says that since this study suggests the possibility of an association between influenza and autism, it reinforces the recommendation that pregnant women should get a flu shot, as recommended by the CDC.


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