Summary:
A nationwide cohort study tracking 3.7 million births over three decades reveals that congenital TORCH infections significantly increase the risk of autism spectrum disorder and intellectual disability in children. While these transplacental infections remain rare at the population level, approximately one in five children born with a diagnosed TORCH infection later developed autism.
Key Facts:
- Elevated Relative Risks: Children with a congenital TORCH infection were roughly three times more likely to be diagnosed with autism, over seven times more likely to be diagnosed with intellectual disability, and faced an up to 30-fold increased risk of severe to profound intellectual disability compared to uninfected peers.
- Rigorous Sibling Comparison: The heightened neurodevelopmental risks persisted after comparing affected children to their uninfected full siblings, confirming that the associations are driven by the infections rather than shared familial genetics or socioeconomic environments.
- Long-Term Academic Impact: Pathogens showed no clear association with ADHD or obsessive-compulsive disorder, but even infected children without a clinical neurodevelopmental diagnosis showed measurably lower school grades on average.
Source: Karolinska Institutet
Certain maternal pathogens have the rare but perilous ability to cross the placental barrier and directly infect a developing fetus. Collectively designated as TORCH, encompassing Toxoplasma gondii, Others (such as syphilis), Rubella, Cytomegalovirus (CMV), and Herpes simplex virus (HSV), these pathogens are known causes of congenital complications.
While their link to structural brain injury and intellectual deficits is historically established, their precise relationship to psychiatric and neurodevelopmental conditions like autism spectrum disorder (ASD) has remained uncertain due to small sample sizes in prior studies.
Now, in the largest epidemiological analysis of its kind, researchers from Karolinska Institutet have tracked nearly an entire nation’s population to quantify these long-term neurodevelopmental risks.
The findings were published in JAMA Pediatrics.
“It is important to emphasise 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,” said Reneé Gardner, Ph.D., a researcher at the Department of Global Public Health at Karolinska Institutet and study co-author.
A Three-Decade Population Cohort
The investigators utilized Sweden’s comprehensive national health registers to evaluate 3.7 million individuals born between 1987 and 2021. Among this massive cohort, 975 children were diagnosed with a congenital TORCH infection at birth. Participants were tracked across health, psychiatric, and educational records for up to 30 years.
The findings demonstrated substantial relative risk increases:
- Children born with a congenital TORCH infection faced a threefold higher risk of receiving an autism diagnosis later in life.
- The risk of developing an intellectual disability was over seven times higher, with the risk of severe to profound intellectual disability surging to up to 30 times higher.
- Overall, researchers estimated that approximately one in five children born with a TORCH infection went on to develop autism.
“It has long been known that these infections can cause intellectual disability. However, the link to autism has been less clear in previous research, which has often been based on small patient groups. This study is the largest to date in this field and is based on national register data covering almost the entire population of Sweden,” explained Hugo Sjöqvist, lead author and doctoral researcher at Karolinska Institutet.
Familial Factors and Specificity of Brain Vulnerabilities
To ensure that unmeasured genetic liabilities or shared household environments were not confounding the results, the researchers conducted within-family sibling comparisons. When comparing children with congenital TORCH infections to their uninfected siblings, the elevated risks for autism and intellectual disability remained consistent, underscoring the direct impact of the pathogens on fetal brain development.
Interestingly, the neurodevelopmental footprint of TORCH pathogens showed high specificity. The researchers found no notable link between congenital infections and conditions such as attention-deficit/hyperactivity disorder (ADHD) or obsessive-compulsive disorder (OCD).
However, fetal infection exerted broader cognitive consequences that extended beyond clinical diagnostic thresholds: even children who did not receive an autism or intellectual disability diagnosis achieved lower average academic marks compared to unexposed peers.
Public Health and Prevention
Because maternal-to-fetal transmission of TORCH pathogens is rare, their overall contribution to population-wide neurodevelopmental conditions remains modest. The study estimates that congenital TORCH infections account for approximately 1.2 percent of all cases of severe intellectual disability and about 0.034 percent of all autism cases across Sweden.
Nevertheless, researchers emphasize that these findings represent an actionable public health priority because many TORCH infections are preventable through proactive clinical and behavioral measures.
“Our results suggest that certain infections transmitted to the fetus during pregnancy may have long-term effects on brain development. Although these congenital infections are rare, some of them can be prevented, which makes them important from a public health perspective,” Gardner highlighted.
The researchers highlighted the success of the MMR vaccine, which has virtually eliminated congenital rubella in Sweden, as proof of how preventative medicine can safeguard neurodevelopment.
Preventative strategies outlined by the research team include:
- Toxoplasmosis: Thoroughly cooking meat, washing produce, and delegating or exercising strict hygiene when handling cat litter.
- Other (Syphilis, etc.): Routine antenatal screening and prompt antibiotic treatment during pregnancy.
- Rubella: Pre-conception screening and routine MMR vaccination.
- Cytomegalovirus (CMV): Rigorous hand hygiene, particularly avoiding direct contact with the saliva and urine of toddlers and young children.
- Herpes Simplex Virus (HSV): Timely detection, prophylactic antiviral treatment, and cesarean delivery when active genital lesions are present near labor.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this Autism Research:
- Media Contact: Press Office
- Source: Karolinska Institutet
- Image Credit: Image credited to Neuroscience News
- Original Research is 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 (toxoplasmosis, syphilis, rubella, cytomegalovirus, or herpes simplex) infections are established causes of severe fetal injury, yet their population-level contribution to neurodevelopmental and psychiatric outcomes, independent of familial confounding, remains yet to be quantified.
Objective
To investigate whether congenital TORCH infections are associated with neurodevelopmental and psychiatric outcomes, including autism and intellectual disability, as well as academic performance, using population-based and sibling-controlled analyses.
Design, Setting, and Participants
This nationwide, population-based cohort study with sibling comparisons was conducted using linked data from Swedish national health, birth, insurance, education, and death registers. Individuals born in Sweden between 1987 and 2021, including individuals diagnosed with a congenital TORCH infection, were included. Full siblings were identified for within-family comparisons. Individuals were followed up from birth until death, emigration, or December 31, 2023. Data were analyzed from November 2025 to July 2026.
Exposure
Clinically diagnosed congenital TORCH infections, identified from national registers, including cytomegalovirus, Toxoplasma gondii, rubella, and herpes simplex viruses.
Main Outcomes and Measures
Autism (with and without co-occurring intellectual disability), intellectual disability (by severity), attention-deficit/hyperactivity disorder, obsessive-compulsive disorder, Tourette and chronic tic disorders, nonaffective psychosis, and standardized school grades at age 16 years were assessed. Associations were estimated with hazard ratios (HRs) using Cox regression and sibling-comparison models.
Results
Among 3 666 002 individuals born in Sweden, including 3 665 027 individuals without TORCH infections (1 883 911 male [51.4%]; mean [SD] follow-up, 20.50 [11.15] years) and 975 individuals with TORCH infections (532 male [54.6%]; mean [SD] follow-up, 18.70 [10.39] years), congenital TORCH infections were associated with increased risks of intellectual disability (HR, 7.22; 95% CI, 6.14-8.49) and autism (HR, 3.10; 95% CI, 2.55-3.76), with similar or greater HRs in sibling comparisons (intellectual disability: HR, 11.28; 95% CI, 5.97-21.33; autism: HR, 3.19; 95% CI, 1.97-5.15). Risks increased with greater severity of intellectual disability, with HRs ranging from 3.01; 95% CI, 2.21-4.11 for mild to 23.51; 95% CI, 18.06-30.60 for severe to profound intellectual disability) and were greater for autism with (HR, 6.23; 95% CI, 4.69-8.28) vs without (HR, 1.97; 95% CI, 1.51-2.57) co-occurring intellectual disability. No consistent associations were observed for obsessive-compulsive disorder, and associations with attention-deficit/hyperactivity disorder attenuated in sibling analyses. Individuals who were exposed had lower school grades in adolescence (TORCH-associated decrease = −1.50 points; 95% CI, −2.60 to −0.40 points).
Conclusions and Relevance
In this study, congenital TORCH infections were rare but associated with intellectual disability and autism, with evidence of broader associated cognitive outcomes extending beyond diagnosed conditions, underscoring the importance of preventing specific vertically transmitted infections.
