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Wednesday 17th July 2019

Flu in pregnancy linked to infant autism

13th November 2012

Danish researchers have found that children have a slightly higher risk of an "infantile autism" diagnosis if their mothers had influenza or a long-running fever during pregnancy.


Such children had a raised risk of diagnosis of autism by the age of three, but their overall risk of an autism spectrum disorder diagnosis was no higher than other children.

It is thought that infection with flu virus could affect the developing brain of the unborn baby, according to a research team at Denmark's Aarhus University.

But study lead author Hjordis Osk Atladottir said the findings should be treated with caution, because of statistical limitations inherent in the study.

She said that 99% of women who got the flu during pregnancy did not go on to have an autistic child.

She said the research was still early and "exploratory," adding that people should not modify their behaviour because of it.

Atladottir's team used data from a study including more than 100,000 pregnant Danish women garnered between 1996 and 2002.

The women were monitored by phone calls from researchers, who asked them about illnesses, infections and medications they had taken.

The latest study compiled data from 96,736 children born from that group of women, who were aged between 8 and 14 years old when the analysis was carried out.

Out of all Danish children during that period, 1% received a psychiatric diagnosis, according to nationwide psychiatric records, and 0.4% of those had infantile autism, meaning that their symptoms became apparent before the age of three.

A range of infections in pregnancy appeared to have no link to autism or infantile autism, including herpes, coughs and colds and cystitis, Atladottir's team found.

Writing in the journal Pediatrics, they reported that seven babies were diagnosed with infantile autism among the 808 women who reported getting influenza (0.87%), compared with 0.4% among the mothers who did not.

The team also identified a borderline increase in risk of autism among women who sustained fevers for more than a week, and those who took some kinds of antibiotics.

Previous research in rodents appears to suggest that activated immune cells can cross the placenta and affect chemicals in a foetus' brain, but Atladottir said it was still not known how such a mechanism might operate in humans.

The researchers said the manner in which they calculated the statistics in the study weakened the findings, as did the fact that the women's infections with "influenza" were not confirmed by doctors.

This meant that the women could have mistaken the flu for a different kind of infection.

Atladottir said further research would be needed to expand on the findings, and that women should not panic.

But Paul Patterson, who studies the immune system and brain development at the California Institute of Technology in Pasadena, said it was highly recommended that women avoid infection during pregnancy, and that there are a variety of very practical ways to minimise this risk.

Pregnant women in the US are advised to get a flu jab, because serious complications with influenza are more common among pregnant women.


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