Background: While no singular cause has been identified for Autism Spectrum Disorder (ASD), research points to several risk factors. These include patterns in genetics as well as in external environmental conditions. One question under debate by researchers is whether infections during pregnancy could increase the risk of ASD in the resulting offspring. Multiple studies have investigated this theory, with conflicting results. To better understand a larger trend in smaller studies, researchers will sometimes conduct a meta-analysis – combining the results of the studies to create a bigger picture of the study effect in action. This statistical approach is especially useful when individual reports disagree in their conclusions.

What’s New: On June 6, 2016, Brain, Behavior, and Immunity published a meta-analysis of 15 studies examining the link between maternal infections and ASD risk. In total, the researchers evaluated data from more than 40,000 ASD cases studied between 2004 and 2015. Within the larger group, individual studies focused on viral, bacterial and fungal infections impacting women during all three trimesters of pregnancy. In combining all these data, the researchers observed a 12 percent increase in the risk of an ASD diagnosis in the offspring of mothers who experienced an infection during pregnancy. The effect was most pronounced among expectant mothers who were in their second trimester of pregnancy, whose infections led to hospitalization, and among those with bacterial infections of the skin or urinary tract. Viral infections during pregnancy and infections during the first trimester, however, were not associated with increased ASD risk.

Why it’s important: Following conflicting evidence in previous studies, this study suggests that babies born to mothers who experienced certain types of infections during pregnancy may in fact have a higher risk of being diagnosed with ASD. Of note, risk severity depended on the time of infection exposure (first, second or third semester) and the site of infection. With large enough sample sizes, future studies could more definitively prove or disprove that link – focusing especially on bacterial infections leading to hospitalization.

Risk Factors

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