Rare pregnancy infections linked to autism
Infections that, in rare cases, can be transmitted from the pregnant woman to the foetus are linked to an increased risk of autism and intellectual disability in the child. This is shown by a study from the Karolinska Institute 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,” says Reneé Gardner, a researcher at the Department of Global Public Health at Karolinska Institutet, who contributed to the study.
The researchers have investigated how so-called TORCH infections affect children’s later development. TORCH is a group of infections that can be transmitted from a pregnant woman to the foetus and includes, amongst others, cytomegalovirus, rubella, toxoplasma and herpesvirus. Unlike many common infections, these pathogens can sometimes cross the placenta and directly infect the foetus.
Were followed for three decades
The study included 3.7 million people born in Sweden between 1987 and 2021. Of these, 975 had been diagnosed with a congenital TORCH infection. The researchers followed the participants for up to three decades to investigate whether the infections were linked to later diagnoses and educational outcomes.
The results show that children with a congenital TORCH infection were approximately three times more likely to be diagnosed with autism later in life and more than seven times more likely to be diagnosed with an intellectual disability compared with children without the infection. The risk of severe to profound intellectual disability was up to 30 times higher.
However, despite the high relative risks, the significance of these infections at a population level is limited, as they are rare in newborns. The researchers estimate that congenital TORCH infections may be linked to approximately 1.2 per cent of all cases of severe intellectual disability, whilst around 0.034 per cent of all cases of autism in Sweden can be explained by these infections. They also estimate that approximately one in five children born with a TORCH infection may later 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,” says Hugo Sjöqvist, a PhD student and lead author of the study.
To better determine whether the associations were due to the infections themselves, the researchers also compared children who had had a TORCH infection with their own siblings who had not had the infection. The results were similar in the sibling comparisons, which suggests that the associations cannot be explained solely by factors shared within families.
The researchers found no clear links between TORCH infections and other neuropsychiatric conditions, such as ADHD or obsessive-compulsive disorder. However, an impact on academic performance was observed. Even children who had not been diagnosed with autism or an intellectual disability had, on average, lower grades than their peers without the infection.
“Our results suggest that certain infections transmitted to the foetus 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,” says Reneé Gardner.
The researchers particularly emphasise the importance of preventive measures. For example, the study points out that rubella has virtually disappeared in Sweden following the introduction of national vaccination programmes. According to the researchers, the results underline the importance of maintaining vaccination programmes and other strategies to prevent infections that can be transmitted from the pregnant woman to the foetus.
The research was funded by the Swedish Research Council. Co-author David Mataix-Cols states that he has received author’s fees from UpToDate Inc and that he is a partner in Scandinavian E-Health AB, which is unrelated to the publication.
Publication
”Congenital TORCH infections and neurodevelopmental outcomes: A population- and sibling-based cohort study”, Hugo Sjöqvist, Christina Dalman, David Mataix-Cols, Reneé M Gardner, Håkan Karlsson, JAMA Pediatrics, online September 21, 2026, doi: 10.1001/jamapediatrics.2026.4229
Facts on how TORCH infections can be prevented
• T = Toxoplasma: Avoid raw or undercooked meat, wash vegetables, and take care when handling cat faeces.
• O = Other (including infections such as syphilis): Screening during pregnancy and antibiotic treatment.
• R = Rubella: Vaccination before pregnancy (MMR vaccine).
• C = Cytomegalovirus (CMV): Good hand hygiene; avoid contact with young children’s saliva and urine.
• H = Herpes simplex (HSV): Identification and treatment of infection during pregnancy; sometimes a caesarean section is performed in the event of active genital herpes prior to delivery.