Flu during pregnancy: Does it affect a child’s mental health?

Clinical takeaway: Maternal influenza during pregnancy was linked to a small increase in neuropsychiatric diagnoses in offspring in population-level analyses, but the association was no longer seen when exposed children were compared with their own unexposed siblings, suggesting that shared familial factors may explain much of the observed risk.

Maternal infection has long been suspected of influencing fetal brain development, and prior studies have reported possible links between prenatal influenza exposure and conditions such as ADHD and autism. However, results have been inconsistent, raising concerns that genetic, socioeconomic, or other family-level factors could be driving the associations rather than a direct effect of infection itself.

In a binational cohort study, researchers analyzed more than 2.56 million mother-child pairs from South Korea and nearly 182,000 pairs from Japan. Influenza during pregnancy was identified in 1.4% of pregnancies in the Korean cohort and 6.2% in the Japanese cohort. Children exposed to maternal influenza had about a 9% to 10% higher risk of receiving any neuropsychiatric diagnosis than unexposed peers in weighted population analyses.

The signal was strongest for ADHD, with risks 13% higher in South Korea and 26% higher in Japan. In the Korean cohort, maternal influenza was also associated with a 37% higher risk of obsessive-compulsive disorder. No significant associations emerged for severe neuropsychiatric disorders, autism spectrum disorder, or intellectual disability. Associations were somewhat stronger when infection occurred during the first trimester, where offspring risk of any neuropsychiatric disorder was 18% higher than in unexposed pregnancies.

But the story changed in sibling-comparison analyses, which included more than 33,000 Korean and nearly 8,000 Japanese exposure-discordant sibling pairs. In those analyses, the increased risk of any neuropsychiatric disorder disappeared, and associations with ADHD, OCD, autism spectrum disorder, and severe psychiatric disorders were no longer significant.

As the authors concluded, “the population-level association should be interpreted cautiously, as our findings suggest that familial factors may partly account for the observed association.”

Source: Kong J, et al. (2026 Oct 8) JAMA Netw Open. Maternal Influenza Infection During Pregnancy and Neuropsychiatric Disorders in Offspring