A large Swedish study published in JAMA Pediatrics on September 21 found that children born with rare infections passed from mother to fetus during pregnancy were significantly more likely to develop autism and intellectual disability later in life.
The research followed nearly 3.7 million people born in Sweden across more than three decades, making it the largest investigation of its kind to date.
The infections belong to a clinical group known as TORCH, a collection of pathogens that can sometimes cross the placenta and reach the developing fetus. They are not the same as the common illnesses many people experience during pregnancy.
While the infections are rare as congenital diagnoses, researchers found that children who were affected faced higher risks of developmental challenges. The findings also come with an important distinction: these infections may raise risk for some children, but they represent only a small portion of autism and intellectual disability cases overall.
Children With These Infections Were Three Times More Likely to Develop Autism
The autism finding in the study is specific to the 975 people in the cohort diagnosed with a congenital TORCH infection at birth, not to children or pregnancies broadly.
Children born with one of these infections were roughly three times more likely to receive an autism diagnosis later in life than children without them. Researchers also estimated that around one in five children born with a TORCH infection may develop autism over time. That figure applies only to the affected group, not to the wider population.
Lead author Hugo Sjöqvist, a PhD student at Karolinska Institutet, said the autism connection had been difficult to establish in earlier studies: “The link to autism has been less clear in previous research, which has often been based on small patient groups.”
Using Swedish national registry data, which covers nearly the full population, allowed researchers to examine a much larger group than previous investigations. At the same time, the study found no association between congenital TORCH infections and either ADHD or obsessive-compulsive disorder.
The Intellectual Disability Risk Was Even More Pronounced
The intellectual disability numbers were stronger than the autism figures, and the effects showed up in children who never received any formal diagnosis at all.
Children with congenital TORCH infections were more than seven times more likely to be diagnosed with intellectual disability than uninfected peers. For severe to profound intellectual disability, the associated risk reached up to 30 times higher. Researchers estimated that these infections may account for about 1.2 percent of severe intellectual disability cases in Sweden.
The effects also showed up in school performance. Children with congenital TORCH infections had lower average grades than their peers, including children who never received a diagnosis of autism or intellectual disability. About 420 people in the study with a diagnosed TORCH infection had lower academic performance without either label, suggesting that developmental effects may extend beyond formal diagnoses.
Related: 15 Ways to Think About Pregnancy That Show Just How Crazy the Human Body Really Is
Why This Finding Does Not Explain Most Autism Cases
The relative risks are substantial. So is the caveat the researchers attach to each one.
Save this article
Enter your email address and we'll send it straight to your inbox.
Reneé Gardner, a researcher in Karolinska Institutet’s Department of Global Public Health, explained: “It is important to emphasize that 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.”
The study estimated that congenital TORCH infections may explain approximately 0.034 percent of autism cases in Sweden. A large increase in risk within a specific group does not mean the infections explain most autism cases in the population. Instead, the findings highlight a connection among children who experience this rare prenatal infection.
A Sibling Comparison Addressed the Most Obvious Question
Shared genetics or household environment could theoretically inflate the association. The team tested that directly.
Researchers compared children with congenital TORCH infections to their own uninfected siblings and found that the elevated risk remained. This comparison helps reduce the possibility that shared family factors alone explain the association, although the study identifies relationships rather than proving direct causes.
The large Swedish registry and the sibling analysis gave researchers a way to examine the connection from multiple angles. Earlier studies often involved smaller patient groups, which made the relationship with autism more difficult to assess.
These Infections Are Rare, and Several Can Be Prevented
The category includes some well-known pathogens, and the study team says the prevention angle helps explain why rare findings still carry public health weight.
TORCH includes cytomegalovirus, rubella, toxoplasma, and herpesvirus; the broader classification also includes syphilis. These pathogens can infect a fetus even when the pregnant person has no noticeable symptoms.
Prevention approaches depend on the specific infection. Careful hand hygiene and avoiding contact with young children’s saliva or urine may reduce CMV risk. Toxoplasma precautions include avoiding raw meat and taking care with cat litter.
Syphilis can be addressed through pregnancy screening and antibiotic treatment. For herpes simplex, management during pregnancy may involve antiviral treatment or, when active infection is present near delivery, a planned cesarean.
If routine TORCH screening were offered during prenatal care where you live, would you want it, and do you think it should be standard practice?
More Articles You Might Be Interested in:
- 8 Horrific Ways Anxiety Secretly Shapes Life During High-Risk Pregnancy
- The female brain changes during puberty, pregnancy and menopause — and each stage leaves a different mark
- High blood pressure in pregnancy may reveal a health risk that doesn’t end after delivery
