Children who were infected in the womb with a rare group of infections known as TORCH were about three times more likely to be diagnosed with autism, according to a Swedish study of 3.7 million people published Sept. 21 in JAMA Pediatrics. They were also more than seven times more likely to receive an intellectual disability diagnosis. The researchers, from Karolinska Institutet in Stockholm, stress that these infections are uncommon and explain only a tiny share of autism cases.
Of 3.7 million people born in Sweden between 1987 and 2021, only 975 had a diagnosed congenital TORCH infection. The finding matters most for a small group of families, not for most pregnancies, and the study shows an association, not proof that the infections directly cause autism.
For expecting parents, the useful message is about prevention. Some TORCH infections can be avoided through vaccination and everyday hygiene.
The TORCH Group and How Rare These Infections Are
TORCH is an acronym for infections that can cross the placenta and infect a developing fetus: toxoplasmosis, other infections such as syphilis, rubella, cytomegalovirus (CMV) and herpes simplex virus. Most infections during pregnancy do not reach the fetus this way.
"It is important to emphasize that it is unusual for these infections to be transmitted from mother to child," said Reneé Gardner, a researcher in the Department of Global Public Health at Karolinska Institutet. The team estimates that these infections account for about 0.034% of autism cases in Sweden and about 1.2% of severe intellectual disability cases.
U.S. numbers need careful reading. The Centers for Disease Control and Prevention estimates that about 1 in 200 U.S. babies is born with congenital CMV and that about 1 in 5 of those babies will have birth defects or other long-term health problems, most often hearing loss. Most babies with congenital CMV never develop problems. The Swedish study counted only formally diagnosed infections, which likely include more serious cases.
Study Findings in Plain Numbers
Researchers followed people for up to three decades using national health and education records. Children with a congenital TORCH infection had about three times the likelihood of an autism diagnosis and more than seven times the likelihood of intellectual disability. For severe to profound intellectual disability, the risk was as much as 30 times higher, Medical Xpress reported.
Even children without autism or intellectual disability had lower school grades on average at age 16. The study found no clear links with ADHD or obsessive-compulsive disorder.
"It was already known that TORCH infections could be harmful in terms of intellectual disability, but we were surprised by the magnitude of the risks," lead author Hugo Sjöqvist, a doctoral student at Karolinska Institutet, told Newsweek. He added that the link with autism remained regardless of intellectual disability status.
Strong Association, Important Limits
This was an observational registry study, not an experiment. It can show that diagnosed TORCH infections and autism occur together more often than expected, but it cannot prove the infection caused autism in each child. The team used sibling comparisons to help account for shared family factors, which strengthens the finding but cannot rule out every other explanation.
Because only diagnosed infections were counted, milder or undetected cases were likely missed, which could make the association look stronger than it would be across all infected babies. The study was done in Sweden, where health care, vaccination rates, and testing practices differ from those in the United States. The infections were also grouped together, so risks for individual infections may vary.
The study does not suggest that common infections during pregnancy, such as colds, cause autism.
Prevention Steps for Expecting Parents
Some protections are already routine. Rubella has nearly disappeared in Sweden since national vaccination began, the researchers noted. People planning a pregnancy can ask a clinician to confirm rubella immunity, since the MMR vaccine should be given before, not during, pregnancy.
CMV has no vaccine, but hygiene lowers the chance of infection. Karolinska Institutet advises good hand hygiene and avoiding contact with young children's saliva and urine, such as not sharing food, utensils or cups with toddlers and washing hands after diaper changes. People who work in child care or have toddlers at home may want to discuss CMV with their obstetrician.
For toxoplasma, common guidance includes avoiding raw or undercooked meat, washing produce and having someone else clean cat litter during pregnancy. Syphilis is found through prenatal screening and treated with antibiotics. Pregnant people with fever, rash or flu-like illness should contact their prenatal care provider rather than wait, and any concern about a newborn's hearing, feeding, or development is worth raising with a pediatrician early.
These infections are rare, and several can be prevented. Future research will need to separate risks by specific infection and test whether earlier diagnosis and treatment improve children's outcomes.
Key Questions Answered
What did the Swedish study find?
Children with a diagnosed congenital TORCH infection were about three times more likely to be diagnosed with autism and more than seven times more likely to have an intellectual disability.
Which infections are in the TORCH group?
Toxoplasmosis, other infections such as syphilis, rubella, cytomegalovirus, and herpes simplex virus. These infections can sometimes cross the placenta.
How common are these infections?
In the Swedish study, 975 of 3.7 million people had a diagnosed congenital TORCH infection. They account for a very small share of autism cases overall.
Does this prove TORCH infections cause autism?
No. The study shows a strong association, supported by sibling comparisons, but it cannot prove direct cause in individual children.
Can these infections be prevented?
Some can. Rubella is prevented by vaccination before pregnancy, and CMV risk can be lowered by limiting contact with young children's saliva and urine.
Should pregnant people worry about ordinary colds?
This study does not link common infections like colds to autism. Anyone with fever, rash or illness during pregnancy should contact their prenatal care provider.
Published by Medicaldaily.com
