Children born with a congenital infection from a specific group of pathogens were about three times as likely to be diagnosed with autism.
They were also more than seven times as likely to be diagnosed with an intellectual disability.
That is the finding of a population-based cohort study published in JAMA Pediatrics on September 21, 2026.
It tracked 3.7 million people born in Sweden from 1987 to 2021.
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The pathogens in question are known by the acronym TORCH.
They include toxoplasma, rubella, cytomegalovirus, and herpes simplex, along with syphilis and related agents.
Congenital means the infection was passed from the pregnant person to the fetus and detected around birth.
In the Swedish cohort of about 3.7 million people, only 975 were diagnosed with such an infection, according to the Karolinska Institutet, which led the work.
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What the numbers actually show
Researchers followed the participants for up to three decades.
In the full population, the hazard ratio for autism was 3.10 and for intellectual disability 7.22.
The risk climbed further for the most severe cases.
Severe-to-profound intellectual disability was linked to a hazard ratio above 23.
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Even children who were never formally diagnosed had lower school grades at age 16 than their uninfected peers, Neuroscience News reported based on the study.
The study also used a sibling comparison.
Children with a congenital TORCH infection were compared with their own full siblings who were born without one.
The association with autism and intellectual disability held up in that within-family analysis, which makes it harder to explain the pattern away as shared genetics or a shared home environment.
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The population level
The relative risks are large, but the infections themselves are uncommon.
The authors estimate that congenital TORCH infections account for around 0.034 percent of all autism cases in Sweden and about 1.2 percent of severe intellectual disability cases.
"it is unusual for these infections to be transmitted from mother to child. They account for a very small proportion of all cases of autism in the population, but for those children who are actually affected, we see a clearly elevated risk of both autism and intellectual disability" said Reneé Gardner of the Department of Global Public Health at Karolinska Institutet, in the institute's news release.
Lead author Hugo Sjöqvist, a doctoral researcher at Karolinska Institutet, added that the work "is the largest to date in this field and is based on national register data covering almost the entire population of Sweden."
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How to reduce the risk
Some of the pathogens in the TORCH group already have well-established prevention paths.
Rubella is covered by MMR vaccination before pregnancy.
Syphilis is picked up through routine antenatal blood tests and treated with antibiotics.
Toxoplasmosis exposure is lowered by cooking meat thoroughly, washing produce, and using care with cat litter.
Cytomegalovirus, the most common congenital infection in the group, has no vaccine and no routine screening in pregnancy.
About 1 in 200 babies is born with congenital CMV in the United States, according to the CDC.
The agency recommends that pregnant people reduce contact with young children's saliva and urine.
That means not sharing food, utensils, cups, or pacifiers with a child.
It also means washing hands with soap and water after diaper changes or helping a child use the toilet.
Anyone who is pregnant or planning a pregnancy and has questions about infection risk, vaccination history, or symptoms should raise them with their obstetric provider before the next prenatal visit.
This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.