Could having the flu in pregnancy lead to autism? Experts weigh in

Our understanding of autism has evolved significantly since the term was first introduced in 1911, with autism spectrum disorder (ASD) today not typically viewed as an “illness” or “disease,” according to the UK’s NHS, but rather as a set of traits that vary widely in type and severity.

Yet despite this progress, scientists are still striving to understand many aspects of the condition.

This includes the underlying causes that contribute to autism or increase the likelihood of its occurrence, though current research primarily points to a combination of genetic and environmental factors.

One such factor is infection during pregnancy, such as influenza, which has been the focus of extensive studies in both animal models and humans.

While this connection may not necessarily be causal, meaning contracting the flu during pregnancy does not guarantee a child will develop autism, research indicates that such infections could be a contributing factor.

Does having the flu during pregnancy lead to autism?

“Our work suggests that women who have febrile episodes, who have high titers of antibodies that go up to herpes simplex type 2, who report influenza and have documentation of influenza are all at higher risk of having children who will subsequently receive an ASD diagnosis,” Dr Ian Lipkin, the director of Columbia University’s centre for infection and immunity, told Euronews Health.

Lipkin was the senior author of a study that explored the potential link between getting the flu during pregnancy and the risk of autism in children.

The study focused on laboratory-confirmed flu cases, rather than relying solely on survey responses or medical records and found some evidence of increased risk of ASD when laboratory-diagnosed influenza was accompanied by self-reported severe symptoms.

“None of this is terribly surprising,” Lipkin said. “I mean, we tell women not to drink during pregnancy, not to take certain drugs during pregnancy, not to smoke during pregnancy, so why would we be surprised that another environmental factor might not also be important in challenging normal foetal development”.

The authors said if infections were contributing to an increased risk of autism, it may not be due to the virus itself but rather to the mother’s immune system’s response and the inflammation it triggered.

Why might virus infections in pregnancy lead to autism?

To better understand what happens to the foetus when the mother gets an infection that leads to autism, researchers have studied animal models.

Dr Irene Sanchez Martin, who is a postdoctoral researcher at the Cold Spring Harbor Laboratory in the US, recently presented findings from her ongoing animal-based study that looks into how inflammation during pregnancy may contribute to neurodevelopmental disorders in children.

Her research, she told Euronews Health, was done on mice models and found that maternal immune activation (MIA) during pregnancy is linked to behavioural outcomes similar to what could be translated as autism in humans.

“We cannot say that a mouse has autism because it’s a different syndrome, but they can displace some behaviour, abnormalities, that can be associated with neurodevelopmental disorders, that usually are autism as well as schizophrenia,” she explained.

The research also focused on studying the immediate effects of exposing pregnant mice to viruses, which Sanchez Martin said could be equivalent to approximately the first trimester in humans.

It showed that once the mother’s immune system was activated after simulating infections, there were early signs of developmental deficits in embryos even within 24 hours of exposure.

Interestingly, the developmental deficits were mostly present in male embryos rather than female ones, she said.

‘The inflammation, not the specific infectious agent’

While Sanchez Martin emphasised that these results may not fully translate to humans due to the use of mouse models, she added that they could bring into light components that help explain factors that lead to autism, given that mice studies allow for comparisons between embryos from the same mother.

The findings were that disruptions to the foetus’ environment like amniotic fluid or the placenta could explain why some were at higher risk of abnormalities in development.

“Basically, this makes us understand that it’s inflammation that is the factor that is associated with these problems,” Sanchez Martin said.

Lipkin also added that “elevated levels of cytokines associated with inflammation” were common in women who have children who were subsequently diagnosed with autism.

“So we think that it’s the inflammation, not the specific infectious agent, and there are many ways in which those can be triggered,” he said.