When an Infection Reaches a Baby Before Birth: What a Study of 3.7 Million Swedes Tells Families About Learning and Development

A plain-language guide to Sjöqvist et al. (JAMA Pediatrics, 2026) on congenital TORCH infections, intellectual disability, autism and school grades

A few babies catch an infection from their mother before or around birth, most often a common virus called cytomegalovirus. A Swedish study of everyone born in the country over 35 years found that these rare infections, when diagnosed by doctors, were linked to higher chances of intellectual disability and autism, even when children were compared with their own brothers and sisters. Most affected children had neither condition.

Why this question matters to families

When a newborn is diagnosed with an infection caught in the womb, parents want to know what it means for their child's future. Will my baby learn to talk and read like other children? Is autism more likely? Doctors have long known that some of these infections can affect the developing brain. What they have not had is good information on how often this happens, which problems are more common and which are not. This article explains what a very large new study found and what it does and does not mean for families.

A long history, starting with German measles

A team at Karolinska Institutet and Region Stockholm in Sweden carried out the new study [1]. It deals with a group of infections that doctors call "TORCH". The letters stand for the main germs involved: toxoplasmosis (caused by a tiny parasite), "other" infections, rubella (German measles), cytomegalovirus (CMV) and herpes [2]. Doctors also count syphilis and several other germs as part of this group [3]. Each of these germs can get past the placenta, the organ that normally protects the baby during pregnancy, and cause what doctors call a congenital infection, meaning one that is present at birth [2].

The story begins with rubella. In the 1950s, doctors described rubella in pregnancy as a cause of what was then called "mental deficiency", which we now call intellectual disability [4]. Intellectual disability means lasting difficulty with learning, reasoning and everyday skills. In 1971, a researcher named Chess reported autism in children born with rubella [5]. Autism is a lifelong difference in how a person communicates, relates to others and experiences the world. In a follow-up study of 243 children with congenital rubella, 37 in every 100 had intellectual disability at preschool age and 7 in every 100 had autism [6]. Rubella vaccination later made this infection very rare in countries like Sweden, and in this study rubella diagnoses almost disappeared from the late 1990s [1].

Since then, CMV has become the most important of these infections. About 1 in 200 babies is born with it, but only around 10 to 15 in every 100 of those babies show signs of illness [7]. Earlier studies linking CMV to autism were either very small or did not account for family background. One large US study using health-insurance records found more autism diagnoses among children with CMV, but it could not compare brothers and sisters [8].

A second puzzle also shaped this study. Earlier work by the same Swedish group looked at ordinary, everyday infections that mothers had during pregnancy. Those infections seemed slightly linked to autism, but the link mostly disappeared when brothers and sisters were compared [9]. A UK study found the same pattern [10]. This suggested that something shared within families, such as genes or home life, explained the link, not the infection itself. Researchers call this "familial confounding" [11]. No one had yet checked whether the same was true for the rarer TORCH infections.

How the study worked

The researchers did not see or test any children. Instead, they used Sweden's national records, which follow every resident from birth. These records include births, hospital and specialist diagnoses, school grades and deaths. The study covered 3,666,002 people born in Sweden between 1987 and 2021 and followed them until the end of 2023, death or moving abroad [1].

Of these, 975 people had a doctor-diagnosed TORCH infection, fewer than 3 in every 10,000 births. About half (487) had CMV. Some infections were only identified later in childhood. For example, if a child was found to have hearing loss, doctors in Sweden could test the tiny blood sample taken at birth for the routine newborn heel-prick test, which is kept in storage. Using this method, one Stockholm team found CMV in about 1 in 5 children with unexplained hearing loss [12].

The researchers compared the children who had an infection with everyone else. They also compared each affected child with brothers and sisters born to the same parents who did not have the infection. Because siblings share much of their genes and home life, this "sibling comparison" helps show whether the infection itself, and not the family, explains any difference.

What the researchers found

The clearest finding concerned intellectual disability. About 15 in every 100 children with a TORCH infection (148 of 975) were later diagnosed with it, compared with about 1 in 100 other people [1]. The more severe the disability, the stronger the link. After the researchers accounted for differences between the groups, a child with an infection was about 7 times as likely to receive this diagnosis.

Autism was also more common: about 10 in every 100 children with an infection (102 of 975) were diagnosed, compared with about 3 in 100 other people. This is roughly three times the usual chance. The increase was largest for autism that occurs together with intellectual disability. Importantly, both links held up when children were compared with their own brothers and sisters. This makes it more likely that the infection itself plays a part.

Other findings were reassuring. There was no consistent link with ADHD (attention-deficit/hyperactivity disorder, which affects attention and activity levels) or with OCD (obsessive–compulsive disorder, which involves unwanted repeated thoughts and behaviours). Teenagers who had an infection but no autism or intellectual disability had slightly lower school grades at age 16, on average 1.5 points lower on a scale where the average is 100. Looking at the germs one by one, only rubella and CMV showed a clear difference. When siblings were compared, the difference was similar in size but too uncertain to be sure of.

Keeping the numbers in proportion

Two points help keep these findings in perspective. First, most children with a diagnosed infection had neither intellectual disability nor autism: about 85 in 100 were not diagnosed with intellectual disability, and about 90 in 100 were not diagnosed with autism. Second, because these infections are rare, they explain only a tiny share of all intellectual disability and autism in Sweden. If the links are truly caused by the infections, the infections account for about 2 in every 1,000 cases of intellectual disability and about 3 in every 10,000 cases of autism [1]. The authors also gave a model-based figure of one new autism case for every five children with an infection. That figure comes from a mathematical model with no stated time frame, and it is not the share of affected children who develop autism. What was actually observed is that about 1 in 10 children with an infection were diagnosed with autism.

What the study cannot tell us

This study counted only infections that doctors diagnosed, usually because the baby was unwell. Sweden does not test all newborns for these infections. The results therefore do not tell us about babies found through newborn screening programmes who seem healthy. Where screening is in place, these babies are expected to make up most of those found to have CMV [7]. The study also did not look at whether treatment changed outcomes. Comparing siblings removes many family influences, but not all: brothers and sisters can still differ in ways that matter [13]. The sibling results were also based on fairly small numbers. Finally, a reader has asked the authors to clarify how some of the follow-up time figures in the paper fit together, and no reply had been published at the time of writing.

What this means for your family

If your baby has been diagnosed with a congenital infection, this study supports regular developmental check-ups as your child grows, including checks on hearing, learning and communication, and support at school if needed. Developmental differences found early can be supported early. It is equally important to know that most children in this study did not develop intellectual disability or autism, and that ADHD and OCD were not consistently linked. Your child's own care team is best placed to explain what the infection means in your child's case. You can read more about newborn CMV screening and CMV treatment on In[Neo]Sight.

What researchers are working on next

The authors say the results underline how important it is to prevent these infections, especially CMV, for example through vaccination where it is available. Rubella shows that this can work. Researchers are also studying ways to prevent CMV from reaching the baby during pregnancy, and future studies will follow screened babies with CMV over many years. A commentary published alongside the study notes that about 1 in 31 children in the United States are now identified with autism by age 8 [14]. That figure is a reminder that infections before birth explain only a small part of a much bigger picture.

The bottom line

Infections that reach a baby before birth are rare, but when doctors diagnose them, they are linked to a higher chance of intellectual disability and autism, and to slightly lower school grades. Most affected children have neither condition. Careful follow-up helps children get support early, and prevention, especially of CMV, offers the best hope of fewer affected children in the future.

References

  1. Sjöqvist H, Dalman C, Mataix-Cols D, Gardner RM, Karlsson H. Congenital TORCH Infections and Neurodevelopmental Outcomes. JAMA Pediatr. 2026. doi:10.1001/jamapediatrics.2026.4229 ↩
  2. Megli CJ, Coyne CB. Infections at the maternal-fetal interface: an overview of pathogenesis and defence. Nat Rev Microbiol. 2022;20(2):67-82. doi:10.1038/s41579-021-00610-y ↩
  3. Neu N, Duchon J, Zachariah P. TORCH infections. Clin Perinatol. 2015;42(1):77-103, viii. doi:10.1016/j.clp.2014.11.001 ↩
  4. KIRMAN BH. Rubella as a cause of mental deficiency. Lancet. 1955;269(6900):1113-1115. doi:10.1016/S0140-6736(55)92951-292951-2) ↩
  5. Chess S. Autism in children with congenital rubella. J Autism Child Schizophr. 1971;1(1):33-47. doi:10.1007/BF01537741 ↩
  6. Chess S, Fernandez P, Korn S. Behavioral consequences of congenital rubella. J Pediatr. 1978;93(4):699-703. doi:10.1016/S0022-3476(78)80921-480921-4) ↩
  7. Swanson MR, Haisley LD, Dobyns WB, Schleiss MR. Beyond hearing loss: exploring neurological and neurodevelopmental sequelae in asymptomatic congenital cytomegalovirus infection. Pediatr Res. 2025;98(7):2471-2482. doi:10.1038/s41390-025-04232-5 ↩
  8. Pesch MH, Leung J, Lanzieri TM, et al. Autism Spectrum Disorder Diagnoses and Congenital Cytomegalovirus. Pediatrics. 2024;153(6):e2023064081. doi:10.1542/peds.2023-064081 ↩
  9. Brynge M, Sjöqvist H, Gardner RM, Lee BK, Dalman C, Karlsson H. Maternal infection during pregnancy and likelihood of autism and intellectual disability in children in Sweden: a negative control and sibling comparison cohort study. Lancet Psychiatry. 2022;9(10):782-791. doi:10.1016/S2215-0366(22)00264-400264-4) ↩
  10. Hope H, Pierce M, Gabr H, et al. The causal association between maternal depression, anxiety, and infection in pregnancy and neurodevelopmental disorders among 410 461 children: a population study using quasi-negative control cohorts and sibling analysis. Psychol Med. 2024;54(8):1693-1701. doi:10.1017/S0033291723003604 ↩
  11. Mataix-Cols D, Pol-Fuster J, de la Cruz LF, et al. Familial confounding and causal inference in child and adolescent neurodevelopment and mental health. Lancet Child Adolesc Health. 2026;10(7):533-540. doi:10.1016/S2352-4642(26)00045-300045-3) ↩
  12. Karltorp E, Hellström S, Lewensohn-Fuchs I, Carlsson-Hansén E, Carlsson PI, Engman ML. Congenital cytomegalovirus infection - a common cause of hearing loss of unknown aetiology. Acta Paediatr. 2012;101(8):e357-362. doi:10.1111/j.1651-2227.2012.02711.x ↩
  13. Frisell T, Öberg S, Kuja-Halkola R, Sjölander A. Sibling comparison designs: bias from non-shared confounders and measurement error. Epidemiology. 2012;23(5):713-720. doi:10.1097/EDE.0b013e31825fa230 ↩
  14. Schleiss MR. TORCH Infections in Pregnancy and Autism Spectrum Disorders. JAMA Pediatr. 2026. doi:10.1001/jamapediatrics.2026.4468 ↩