Summary:
A nationwide cohort study spanning more than three decades and including 3.7 million births shows that congenital TORCH infections—those transmitted from mother to fetus—are associated with substantially increased risks of autism spectrum disorder (ASD) and intellectual disability in affected children. Although these infections are rare at the population level, among the small number of infants diagnosed at birth, roughly one in five later received an autism diagnosis.
Key Facts:
- Markedly increased risks: Children with a congenital TORCH infection had about a threefold higher risk of autism, more than a sevenfold higher risk of intellectual disability, and up to a 30-fold greater risk of severe to profound intellectual disability compared with unexposed peers.
- Sibling-controlled findings: These associations remained after comparing affected children with their uninfected full siblings, indicating the links are unlikely to be explained by shared family genetics or socioeconomic factors.
- Broader academic effects: While TORCH infections were not clearly associated with ADHD or obsessive-compulsive disorder, infected children who did not meet diagnostic criteria for neurodevelopmental disorders still averaged lower school grades by age 16.
Source: Karolinska Institutet
Background: Certain maternal infections can cross the placenta and infect the developing fetus. Commonly grouped as TORCH—Toxoplasma gondii, Others (for example syphilis), Rubella, Cytomegalovirus (CMV), and Herpes simplex virus (HSV)—these pathogens have long been linked to structural brain injury and intellectual impairments when transmitted in utero. Their specific relationships with psychiatric and neurodevelopmental conditions such as autism have been less well defined due to limited sample sizes in earlier research.
Researchers at Karolinska Institutet performed the largest population-based analysis to date to quantify long-term neurodevelopmental risks associated with clinically diagnosed congenital TORCH infections. The study’s results were published in JAMA Pediatrics.
“Maternal-to-fetal transmission of these infections is uncommon, so they represent a small share of all autism cases in the population. However, for children who are affected, there is a clearly elevated risk of both autism and intellectual disability,” said Reneé Gardner, Ph.D., a co-author and researcher at the Department of Global Public Health at Karolinska Institutet.
A Three-Decade Population Cohort
The investigators used Sweden’s national health registers to follow 3,666,002 individuals born between 1987 and 2021. Of these, 975 infants were clinically diagnosed with a congenital TORCH infection at birth. Participants were linked across health, psychiatric, and educational records and followed for up to 30 years.
Key relative risk findings from the cohort include:
- About a threefold higher hazard of receiving an autism diagnosis for those born with a TORCH infection.
- More than a sevenfold higher risk of developing intellectual disability, with risk estimates increasing with severity—reaching as much as a 30-fold increase for severe to profound intellectual disability.
- An estimated one in five children born with a TORCH infection were later diagnosed with autism.
Hugo Sjöqvist, lead author and doctoral researcher at Karolinska Institutet, noted that this study is the largest of its kind and benefits from nearly complete national register coverage, strengthening prior observations that were limited to smaller patient groups.
Familial Confounding and Specific Vulnerabilities
To address potential confounding by family-level genetic or environmental factors, the team performed within-family sibling comparisons. Elevated risks for autism and intellectual disability persisted when comparing affected children with their unexposed full siblings, supporting a direct effect of in utero infection on fetal brain development rather than confounding by shared family characteristics.
The neurodevelopmental impact of congenital TORCH infections also showed specificity: there were no consistent associations with obsessive-compulsive disorder, and associations with attention-deficit/hyperactivity disorder weakened in sibling-controlled analyses. Still, cognitive effects extended beyond diagnostic categories: exposed individuals demonstrated lower standardized school grades in adolescence, indicating broader academic consequences.
Public Health Implications and Prevention
Given the rarity of maternal-to-fetal TORCH transmission, these infections contribute only a small fraction of overall autism and intellectual disability cases in the population—estimated in this study as approximately 0.034% of autism cases and about 1.2% of severe intellectual disability cases in Sweden. Nonetheless, many TORCH infections are preventable, making them a meaningful public health target.
The researchers highlighted the successful elimination of congenital rubella in Sweden following widespread MMR vaccination as an example of how prevention protects neurodevelopment. Recommended prevention strategies emphasized in the study include:
- Toxoplasmosis: Thoroughly cook meat, wash fresh produce, and practice careful hygiene around cat litter.
- Other infections (including syphilis): Routine antenatal screening and prompt antibiotic treatment when indicated.
- Rubella: Preconception screening and ensuring up-to-date MMR vaccination.
- Cytomegalovirus (CMV): Careful hand hygiene and avoiding contact with the saliva and urine of toddlers and young children during pregnancy.
- Herpes simplex virus (HSV): Timely diagnosis, antiviral prophylaxis when appropriate, and cesarean delivery if active genital lesions are present close to labor.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- The journal paper was reviewed in full by editorial staff.
- Additional context was provided by the reporting team.
About this Autism Research:
- Media Contact: Press Office
- Source: Karolinska Institutet
- Image Credit: Image credited to Neuroscience News
- Original Research (Open Access): JAMA Pediatrics (September 21, 2026). “Congenital TORCH infections and neurodevelopmental outcomes: A population- and sibling-based cohort study.” Authors: Hugo Sjöqvist, Christina Dalman, David Mataix-Cols, Reneé M. Gardner, and Håkan Karlsson.
- DOI: 10.1001/jamapediatrics.2026.4229
Abstract
Congenital TORCH infections and neurodevelopmental outcomes: A population- and sibling-based cohort study
Importance
Congenital TORCH infections—caused by toxoplasmosis, syphilis, rubella, cytomegalovirus, or herpes simplex—are established causes of severe fetal injury. However, their contribution to neurodevelopmental and psychiatric outcomes at the population level, independent of familial confounding, has not been fully quantified.
Objective
To assess associations between clinically diagnosed congenital TORCH infections and a range of neurodevelopmental and psychiatric outcomes, including autism and intellectual disability, and to evaluate academic performance using both population-based and sibling-controlled approaches.
Design, Setting, and Participants
This nationwide cohort study used linked Swedish registers covering health, birth, insurance, education, and death data. Individuals born in Sweden from 1987 through 2021 were included and followed from birth until death, emigration, or December 31, 2023. Full siblings were identified for within-family comparisons. Data were analyzed from November 2025 to July 2026.
Exposure
Clinically recorded congenital TORCH infections, including cytomegalovirus, Toxoplasma gondii, rubella, and herpes simplex viruses, as identified in national registers.
Main Outcomes and Measures
Measured outcomes included autism (with and without co-occurring intellectual disability), intellectual disability by severity, ADHD, OCD, Tourette and chronic tic disorders, nonaffective psychosis, and standardized school grades at age 16. Associations were estimated with hazard ratios using Cox regression and sibling-comparison models.
Results
Among 3,666,002 individuals, 975 had a congenital TORCH diagnosis. Congenital TORCH infections were associated with increased risks of intellectual disability (HR, 7.22) and autism (HR, 3.10), with sibling comparisons showing similar or larger hazard ratios. Risks rose with intellectual disability severity and were higher when autism co-occurred with intellectual disability. No consistent associations were found for OCD, and ADHD associations diminished in sibling analyses. Exposed individuals also had lower school grades in adolescence.
Conclusions and Relevance
Although rare, congenital TORCH infections are linked to higher risks of intellectual disability and autism and to broader adverse effects on cognitive and academic outcomes. These findings reinforce the importance of prevention strategies for specific vertically transmitted infections to protect fetal brain development and long-term neurodevelopmental health.