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Flu during pregnancy not linked to child’s autism risk

Autism no more likely among children whose mothers had flu jab in 2nd or 3rd trimester

Louise Prime

Tuesday, 29 November 2016

Children whose mothers had influenza during pregnancy were at no greater risk of autism spectrum disorders (ASD) than those whose mothers didn’t have flu prenatally, research* published online today by JAMA Pediatrics has shown. The study’s authors also found no link between vaccination against flu in mid- to late pregnancy and ASD; however, they said there was a suggestion of an increased risk of ASD in children whose mothers were vaccinated in early pregnancy, and they called for further research into this.

Researchers led from Kaiser Permanente Northern California in the US accessed data on 196,929 children who had been born at ≥24 weeks’ gestation in the health system between 2000 and 2010. In this cohort, 1,400 (0.7%) of the mothers had been diagnosed with flu during pregnancy and 45,231 (23%) of mothers had had a flu vaccination during pregnancy. ASD had been diagnosed in 3,101 of all the children.

When they analysed the data, the study authors found no association between ASD and a diagnosis of maternal flu infection at any point during pregnancy. Nor did they find any association between ASD and maternal flu vaccination during the second or third trimesters of pregnancy. They reported a “suggestion” of an increased risk of ASD among children whose mothers had been vaccinated against flu during the first trimester. They said this was likely to be a chance finding, as it became statistically insignificant once they had adjusted for other factors.

They also stressed that their study had several limitations – such as its reliance on medical records for ASD diagnosis – and could not, by design, show causality.

Although the researchers said this meant no policy changes around vaccination are needed now, they called or further research into the association.

They concluded: “We found no association between ASD risk and influenza infection during pregnancy or influenza vaccination during the second to third trimester of pregnancy. However, there was a suggestion of increased ASD risk among children whose mothers received influenza vaccinations early in pregnancy, although the association was insignificant after statistical correction for multiple comparisons. While we do not advocate changes in vaccine policy or practice, we believe that additional studies are warranted to further evaluate any potential associations between first-trimester maternal influenza vaccination and autism.”

* Zerbo O, Qian Y, Yoshida C, et al. Association between influenza infection and vaccination during pregnancy and risk of autism spectrum disorder. JAMA Pediatr. Published online 28 November, 2016. doi:10.1001/jamapediatrics.2016.3609.

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