A large Swedish registry study of nearly 3.7 million births found that the 975 children born with congenital TORCH infections were about three times more likely to be diagnosed with autism and over seven times more likely to have intellectual disability, with risks for severe ID up to 30 times higher. The research used sibling comparisons to reduce family-level confounding and found no link with ADHD or OCD. Although risks for affected children are substantial, TORCH infections are rare and account for only a tiny share of autism cases at the population level.
Rare Prenatal TORCH Infections Linked to Higher Autism and Intellectual Disability Risk, Large Swedish Study Finds
Doctor checking a pregnant woman
A major Swedish registry study published in JAMA Pediatrics on September 21 examined nearly 3.7 million people born in Sweden over more than three decades and found that children diagnosed at birth with congenital TORCH infections faced substantially higher risks of later neurodevelopmental problems, especially intellectual disability.
Key Findings
Out of the full cohort, 975 individuals had a recorded congenital TORCH infection at birth. Compared with uninfected peers, those children were roughly three times more likely to receive an autism diagnosis later in life; the researchers estimated that about one in five (≈20%) children born with a TORCH infection may develop autism over time, a figure that applies only to the affected subgroup.
The associations were strongest for intellectual disability (ID). Children with congenital TORCH infections were over seven times more likely to be diagnosed with ID than uninfected peers, and the risk for severe to profound intellectual disability reached as high as 30 times greater. Based on the data, the authors estimated that congenital TORCH infections could account for roughly 1.2% of severe intellectual disability cases in Sweden.
Population Impact and Context
Although the relative risks are large for affected individuals, these infections are rare. The study estimated congenital TORCH infections may explain approximately 0.034% of autism cases at the population level in Sweden. As the authors emphasized, a high relative risk within a small group does not imply TORCH infections explain most autism cases overall; rather, the findings identify an important risk factor for a narrowly defined set of children.
Methods, Robustness, and Limitations
The investigators used nearly complete national registry data spanning more than three decades, which provided exceptional statistical power compared with earlier small studies. To reduce confounding by family-level factors (shared genetics or household environment), they compared affected children to their own uninfected siblings; the elevated risks remained in the sibling comparison, which strengthens the association though does not prove causation.
Image Credit: Kittyfly/Depositphotos
The study also found no association between congenital TORCH infections and either attention-deficit/hyperactivity disorder (ADHD) or obsessive-compulsive disorder (OCD). The researchers note that registry-based observational studies can identify relationships but cannot definitively establish direct causation.
Education and Subclinical Effects
Beyond formal diagnoses, children born with congenital TORCH infections had lower average school grades than peers. About 420 affected individuals showed reduced academic performance despite not having formal autism or intellectual disability diagnoses, suggesting developmental effects can extend below diagnostic thresholds.
What Are TORCH Infections?
TORCH is a clinical grouping of pathogens that can cross the placenta and infect the fetus. It commonly refers to cytomegalovirus (CMV), rubella, toxoplasma, and herpesviruses, and the broader classification often includes syphilis. These infections can sometimes pass from mother to fetus even when the pregnant person has no noticeable symptoms.
Prevention and Clinical Implications
Prevention strategies vary by pathogen. For CMV, pregnant people are advised to practice careful hand hygiene and avoid contact with saliva or urine from young children. Toxoplasma risk can be reduced by avoiding raw or undercooked meat and taking precautions with cat litter. Routine prenatal screening and antibiotic treatment prevent congenital syphilis, while herpes simplex virus may be managed with antiviral therapy and delivery planning (including cesarean delivery when active lesions are present near term).
Lead author Hugo Sjöqvist (Karolinska Institutet) and colleague Reneé Gardner note that mother-to-child transmission is unusual but, when it occurs, the developmental consequences can be substantial for the affected child.
Bottom Line
The Swedish registry analysis identifies a clear association between congenital TORCH infections and elevated risks of autism and, especially, intellectual disability among the small group of affected children. The findings underscore the value of prevention where possible and the importance of monitoring and early support for children born with congenital infections, while reaffirming that these infections account for only a very small fraction of neurodevelopmental disorder cases at the population level.
Help us improve.
