BOSTON – Children born to mothers infected with COVID-19 during pregnancy may face a higher risk of autism and other developmental differences, according to new research published in the Obstetrics and Gynaecology journal.
The study, based on data from more than 18,000 births within the Mass General Brigham health system in Boston, found that 16 per cent of children exposed to the coronavirus in the womb were later diagnosed with a neurodevelopmental disorder—compared with less than 10 per cent among those whose mothers were not infected. After adjusting for other factors, this represented a 1.3-fold higher risk.
The link was most evident among boys and when infection occurred in the third trimester—a critical stage for brain development. The most common diagnoses included speech and motor delays and autism.
Researchers found that about 2.7 per cent of children born to mothers who had COVID-19 during pregnancy were later diagnosed with autism, compared to 1.1 per cent among those unexposed. While the absolute difference is small, experts said it was statistically meaningful.
“Even a modest increase in risk is important to understand, given how many women worldwide contracted COVID-19 during pregnancy,” the authors noted.
Infection, Not Vaccination, Under Study
Because the research period spanned March 2020 to May 2021—before vaccines were widely available—most mothers in the study were unvaccinated.
This allowed researchers to focus specifically on the effects of the infection itself, rather than vaccination.
Scientists believe the virus rarely crosses the placenta. Instead, they suggest that inflammation and immune responses during infection could subtly affect fetal brain development.
The study’s findings echo earlier evidence that infections in pregnancy—such as influenza—can influence neurodevelopment in children.
However, the researchers cautioned that the results show an association, not proof of direct causation. Other factors, such as illness severity, stress, genetics, and access to prenatal care, may also contribute.
Evidence Still Emerging
A related 2023 study published in JAMA Network Open reached similar conclusions. It analysed more than 18,000 births at the same hospital system and found that babies exposed to maternal COVID-19 infection were nearly twice as likely to be diagnosed with developmental differences by their first birthday.
In that study, 3 per cent of exposed infants had developmental diagnoses compared with 1.8 per cent of those unexposed, with the association again strongest among boys and third-trimester infections.
Researchers proposed that maternal immune activation—specifically increased levels of inflammatory molecules like interleukin-6—may influence the developing brain, even when infections are mild or moderate.
While the relative increase in risk was significant, experts emphasised that the absolute numbers remain small—equivalent to one or two additional neurodevelopmental diagnoses per hundred infants.
Scientists stress that the research is ongoing and that many developmental conditions may not be fully evident by age three.
Longer-term studies will be needed to determine whether these early differences persist or fade over time.
Still, the findings underscore the importance of protecting pregnant women from infection through vaccination and preventive measures.