Of 975 children in Sweden born with a diagnosed congenital TORCH infection, roughly one in five went on to receive an autism diagnosis. That is the number families and doctors will carry away from a large new study in JAMA Pediatrics, published on September 21, 2026.
Researchers at Karolinska Institutet followed 3.7 million people born in Sweden between 1987 and 2021, using the country’s national health, psychiatric and school records, for up to 30 years. It is the largest study of its kind, and it answers a question smaller studies could not settle.
What the numbers show
Children born with a TORCH infection were about three times as likely to be diagnosed with autism. Their risk of intellectual disability was more than seven times higher. For severe to profound intellectual disability, the risk climbed as high as 30 times that of uninfected peers.
“It has long been known that these infections can cause intellectual disability,” said Hugo Sjöqvist, the lead author and a doctoral researcher at Karolinska Institutet. “However, the link to autism has been less clear in previous research, which has often been based on small patient groups.”
The team also compared infected children with their own uninfected full siblings, so that shared genes and a shared home could not explain the gap. The risks held. That points to the infection itself, and its effect on the fetal brain, rather than family background.
The pattern was narrow, too. The researchers found no notable link to ADHD or obsessive-compulsive disorder. But the damage did not stop at formal diagnoses. Infected children who never received an autism or intellectual disability diagnosis still earned lower school grades on average.
Rare, but preventable
TORCH stands for toxoplasmosis, other infections such as syphilis, rubella, cytomegalovirus (CMV) and herpes simplex virus. All can cross the placenta and reach a developing baby.
Co-author Reneé Gardner, a researcher at the Department of Global Public Health at Karolinska Institutet, was careful about the scale. “It is important to emphasise that it is unusual for these infections to be transmitted from mother to child,” she said. The study estimates that they account for about 1.2 percent of severe intellectual disability and about 0.034 percent of autism cases in Sweden. For the children affected, though, she said the risk is clearly raised.
Her point for expectant parents was that some of these infections can be prevented. For toxoplasmosis, the research team advises cooking meat thoroughly, washing produce and taking strict care with cat litter. For syphilis and similar infections, it recommends routine antenatal screening and prompt antibiotics during pregnancy. Rubella calls for screening before conception and routine MMR vaccination. For CMV, the advice is careful hand washing, especially after contact with the saliva and urine of toddlers and young children. For herpes simplex, it is early detection, preventive antiviral treatment, and cesarean delivery when active genital lesions are present near labor.
The MMR vaccine has virtually eliminated congenital rubella in Sweden, the researchers noted. Anyone with questions about their own pregnancy should consult their doctor.
