Rare congenital infections tied to higher autism risk

Clinical takeaway: Reinforce preventive measures against congenital TORCH infections, including vaccination, screening, and infection-avoidance counseling during pregnancy, as these rare infections may have long-term neurodevelopmental consequences for affected children.

TORCH infections (toxoplasmosis, syphilis, rubella, cytomegalovirus [CMV], and herpes simplex virus) are established causes of fetal injury and intellectual disability, but their relationship with autism has remained less certain. This large population-based study helps clarify that association while highlighting the potential importance of preventing infections that can cross the placenta and directly affect the developing fetal brain.

Researchers analyzed data from more than 3.66 million individuals born in Sweden between 1987 and 2021, including 975 diagnosed with a congenital TORCH infection. After up to three decades of follow-up, children with congenital TORCH infections were about three times more likely to be diagnosed with autism and more than seven times more likely to develop intellectual disability than unexposed peers. Risks rose with increasing severity of intellectual disability, with severe-to-profound cases occurring more than 20 times as often among affected children.

The autism association persisted when investigators compared exposed children with their own unexposed siblings, suggesting the findings were not fully explained by shared familial or genetic factors. Children with TORCH infections were also nearly twice as likely to develop autism without intellectual disability and more than six times as likely to develop autism with co-occurring intellectual disability.

Although relative risks were substantial, the infections were rare, occurring in roughly 2.5 per 10,000 births. The authors estimated that approximately 1 in 5 children born with a TORCH infection may later develop autism, yet these infections account for only a very small fraction of autism cases at the population level. Even among children without diagnosed autism or intellectual disability, congenital TORCH infection was associated with modestly lower school performance during adolescence. No clear associations were seen for OCD, and links to ADHD disappeared in sibling analyses.

“Our results suggest that certain infections transmitted to the foetus during pregnancy may have long-term effects on brain development,” said study coauthor Reneé Gardner, PhD. “Although these congenital infections are rare, some of them can be prevented, which makes them important from a public health perspective.”

In an accompanying editorial, Mark Schleiss, MD, highlighted CMV as the most important target for prevention efforts, writing that a future CMV vaccine could have a substantial public health impact and should be viewed as a potential tool to help prevent some cases of autism.

Source: Sjöqvist H, at al. (2026 Sep 21) JAMA Pediatr. Congenital TORCH Infections and Neurodevelopmental Outcomes: A Population- and Sibling-Based Cohort Study