Pregnancy influenza infection not linked to offspring autism

"There was no association between maternal influenza [flu] infection anytime during pregnancy and increased ASD [autism spectrum disorder] risk."

So said the findings reported by Ousseny Zerbo and colleagues [1] continuing a research theme from this author (see here for example) looking at how various infections 'encountered' during critical periods of pregnancy may / may not impact on offspring autism risk. This time around the focus was on viral infections and in particular "maternal influenza infection and vaccination from conception date to delivery date" as derived from either diagnosis using ICD-9 criteria or "a positive laboratory result for influenza based on the Prodesse ProFlu+ Assay (Hologic), a multiplex real-time polymerase chain reaction in vitro diagnostic test." Said participants numbering nearly 200,000 children were all born "at Kaiser Permanente Northern California from January 1, 2000 to December 31, 2010, at a gestational age of at least 24 weeks." The press release accompanying the publication can be seen here.

"Maternal influenza infection during pregnancy was not associated with increased ASD risk in this study, and the association did not vary by the timing of influenza infection." Importantly, authors also looked at whether maternal influenza vaccination during pregnancy was also related to offspring ASD risk based on the data contained in their patient databases. The results pertinent to pregnancy flu vaccination and offspring risk were not exactly cut-and-dried as "in an initial analysis unadjusted for multiple comparisons" the authors reported seeing a 'slightly increased' risk for offspring autism associated with maternal vaccination during the first few months of pregnancy. This was set against data indicating no significant association between maternal influenza vaccination covering 'anytime' during pregnancy. Indeed, after "adjusting for the multiplicity of hypotheses tested" they concluded that the first trimester vaccination - offspring autism risk was potentially a 'chance finding'. Minus any scaremongering and to be on the safe side the authors suggested that "additional studies are warranted to further evaluate any potential associations between first-trimester maternal influenza vaccination and autism."

Aside from a few potential 'weakness' attached to the Zerbo results including the fact that "subclinical infections or illnesses for which women did not seek medical attention" were not counted in the data, these are interesting results. Quite a few times on this blog I've covered the so-called maternal immune activation (MIA) hypothesis - where mum's reprogrammed pregnancy immune system is 'challenged' and potentially has implications for offspring development - and this work kinda falls into that category of autism science. Indeed, I've talked about the possibility quite recently (see here). Drawing also on data looking at season of conception/birth as potentially being important to pregnancy viral/bacterial exposure and onward offspring outcomes (see here) there has been a steady stream of peer-reviewed publications hinting at a potentially important 'association' between infection exposure in-utero and developmental outcomes for the child. The current Zerbo data however put a bit of a research spanner in the works when it comes specifically to any pregnancy flu and offspring autism risk suggestion albeit with the continued requirement for further investigations in this area covering other infections.

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[1] Zerbo O. et al. Association Between Influenza Infection and Vaccination During Pregnancy and Risk of Autism Spectrum Disorder. JAMA Pediatr. 2016 Nov 28.

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Zerbo O, Qian Y, Yoshida C, Fireman BH, Klein NP, & Croen LA (2016). Association Between Influenza Infection and Vaccination During Pregnancy and Risk of Autism Spectrum Disorder. JAMA pediatrics PMID: 27893896