Rare infections during pregnancy linked to higher risk of severe intellectual disability and autism

Children born with infections such as syphilis, rubella and cytomegalovirus are far more likely to be diagnosed with autism and intellectual disability, according to a new study. Children with infections that were transmitted during pregnency are about 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, a new study has found. That signals that certain infections transmitted to the foetus during pregnancy may have long-term effects on brain development, the authors noted. Such infections, known as TORCH – a group of infections that can be transmitted from a pregnant woman to the foetus — include syphilis, rubella, toxoplasmosis, cytomegalovirus and herpesvirus. Unlike many common infections, these pathogens can sometimes cross the placenta and directly affect the foetus, increasing the risk of miscarriage, stillbirth and pregnancy complications. “Although these congenital infections are rare, some of them can be prevented, which makes them important from a public health perspective,” said Reneé Gardner, a researcher at the Department of Global Public Health at the Karolinska Institutet, who contributed to the study. 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. While these infections account for a very small proportion of all cases of autism in the population, children who are affected have an elevated risk of both autism and intellectual disability. One in five children born with a TORCH infection may later develop autism, the authors noted. Beyond autism, being born with such infections was associated with a higher risk of intellectual disability at all levels. The risk of severe to profound intellectual disability was up to 30 times higher than in children without the infection. Even without a diagnosis, the infections appeared to affect educational outcomes. In the study, 420 people were diagnosed with a TORCH infection and performed poorly in school without being diagnosed with autism or an intellectual disability. TORCH infections vary in epidemiology and prevalence. The most prevalent globally is congenital cytomegalovirus (CMV), affecting about one in every 150 newborns. This burden is substantially higher in low- and middle-income countries. How can the risks be reduced? According to the authors, the study underscores the importance of strengthening preventive strategies, particularly in areas with higher infection rates. The study highlights the public health importance of developing, deploying, and maintaining mass vaccination strategies to prevent these infections. The authors also noted that current systems —like the one in Sweden — may miss asymptomatic cases because newborn screening for TORCH is not universally implemented and called for better strategies to identify these cases.