The evidence of influenza A virus infection during pregnancy as a risk factor for neuropsychiatric disorder in offspring

Abstract

To the Editor,

With interest we read the paper about the effects of infection with Influenza A virus on pregnant mice: disruption of maternal intestinal immunity and of foetal cortical development in a time- and dose-dependent manner [1]. However, we were surprised to read in the introduction of the paper that “epidemiological studies demonstrate that influenza A virus infection during pregnancy increases the prevalence of offspring neurodevelopmental disorders like schizophrenia, bipolar disorder and autism spectrum disorder (as reviewed in [2])”. The authors cite three papers that support an association with schizophrenia, one paper that does the same for bipolar disorder and one for autism spectrum disorder. Importantly, they do not mention dozens of studies that obtained negative results. The review cited by the authors [2] describes possible mechanisms that can lead to neuropsychiatric illness and is not a critical or systematic review of the existing epidemiological literature. The authors fail to mention two meta-analyses of studies on the relationship between maternal influenza during pregnancy and risk of schizophrenia or bipolar disorder in the child [3, 4], and a systematic review of studies on a wider range of neuropsychiatric outcomes, including autism spectrum disorder and intellectual disability [5]. Let us very briefly summarize the findings.