No link exists between maternal flu and increased child autism risk, says study

By Sally Robertson, B.Sc.Dec 1 2016

A study has found no association between a mother catching the flu during pregnancy and their child having an increased risk of autism spectrum disorder (ASD).

As reported in JAMA Pediatrics, the study tracked 196,929 children born between 2000 and 2010, at a gestational age of 24 weeks or more. It included 1,400 mothers (0.7%) who had been diagnosed with influenza infection and 45,231 mothers (23%) who had received a vaccination against influenza at some point during their pregnancy. Of all the children born, 3,101 (1.6%) were diagnosed with an ASD.

Lead author Ousseny Zerbo from Kaiser Permanente Northern California and colleagues found no overall link between influenza infection or vaccination at any point during pregnancy and an increased ASD risk in children.

Trimester-specific analysis did suggest an increased risk of ASD among mothers who were vaccinated during the first trimester, but the authors say this could have been due to chance because the finding was statistically insignificant after adjusting for multiple comparisons.

We found no association between ASD risk and influenza infection during pregnancy or influenza vaccination during the second to third trimester of pregnancy,”

Lead author Ousseny Zerbo from Kaiser Permanente Northern California and colleagues.

“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.”

The authors say their study cannot establish causality and had a number of limitations, including ASD status being established by diagnoses on medical records and not having been validated by standardized clinical assessment in all cases. Furthermore, other potential unmeasured mitigating factors could not be controlled for.

“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," concludes the team.