Researchers from the Karolinska Institute have uncovered new evidence showing that rare infections crossing the placenta during pregnancy can triple the risk of autism spectrum disorder in children. Their large-scale study examined nearly 3.7 million births to confirm this important link.
- Study covers nearly 3.7 million Swedish births from 1987 to 2021
- Exposure to rare congenital infections triples autism risk
- Severe intellectual disability risk increases thirtyfold with infection
What happened
A major study led by scientists at the Karolinska Institute in Sweden analyzed data from almost 3.7 million individuals born between 1987 and 2021. Using national medical registers, they identified 975 children exposed to rare infections crossing the placenta during gestation, including toxoplasmosis, syphilis, rubella, cytomegalovirus, and herpes simplex.
By comparing developmental outcomes, researchers found that these prenatal infections were linked to a threefold increase in autism risk. For children with profound intellectual disabilities, the risk rose dramatically, by up to 30 times. The study adjusted for several other factors like birth method and gestational age to strengthen these findings.
Why it feels good
This research brings clarity to a longstanding suspicion about how rare congenital infections may influence neurodevelopment, supporting broader efforts to understand autism’s complex causes. The large population data set allowed scientists to isolate infection as a clear, though rare, risk factor amidst many potential influences.
Importantly, the study emphasizes that infection transmission from mother to fetus is uncommon and represents only a tiny fraction of all autism cases—around 0.034%. However, for affected families, the insights provide a valuable perspective that could eventually inform prevention and care strategies.
What to enjoy or watch next
Continued research into congenital infections and their neurological effects may lead to improved prenatal screening and vaccination initiatives to protect expectant mothers and babies. Keeping common placental infections rare through public health measures will remain a crucial priority.
Those interested in neurological development and prenatal health might follow updates from the Karolinska Institute and global health agencies working to understand how early-life factors shape lifelong outcomes. This study represents an encouraging step toward unraveling autism’s many roots with hope and precision.