Long before a baby draws its first breath, a quiet biological negotiation is already underway — one that may help determine whether that child develops autism. Scientists at the University of Virginia School of Medicine have uncovered compelling evidence that a mother’s gut bacteria during pregnancy can directly influence her unborn child’s susceptibility to autism spectrum disorder (ASD), placing the spotlight squarely on one of the most overlooked corners of prenatal health: the microbiome.
The findings, published in The Journal of Immunology, challenge the conventional focus on genetics as the dominant driver of autism risk. Instead, they suggest that the trillions of microscopic organisms living inside an expectant mother’s digestive tract are doing far more than aiding digestion — they may be actively shaping the architecture of a developing brain.
The Middleman Between Gut and Brain
At the center of this research is an inflammatory molecule called interleukin-17a, or IL-17a. Scientists at MIT previously found that IL-17a can influence the development of autism-like disorders in the brain, and that it has also been found to play a role in multiple sclerosis and rheumatoid arthritis. Newsweek What the UVA team discovered, however, was something more specific and more actionable: the maternal microbiome appears to act as the key regulator of how much IL-17a the immune system produces — and that level of production, in turn, can determine a child’s neurodevelopmental trajectory.
“The microbiome can shape the developing brain in multiple ways,” explained lead researcher John Lukens, of UVA’s Center for Brain Immunology and Glia. “The microbiome is really important to the calibration of how the offspring’s immune system is going to respond to an infection or injury or stress.” ScienceDaily
To understand how, Lukens and his team worked with two groups of mice that had different gut microbiota compositions. One group carried bacteria known to trigger a strong IL-17a-driven inflammatory response; the other did not. When both groups of pregnant mice were exposed to a viral immune challenge — mimicking the kind of infection a pregnant woman might experience — only the offspring of the first group went on to exhibit autism-like behaviors, including repetitive movements and reduced social interaction.
A Transplant That Transferred Risk
Perhaps the most striking phase of the experiment involved fecal transplantation — the transfer of gut bacteria from one group of mice to another. Researchers cohoused the two sets of mice, effectively enabling microbiota transfer since mice consume each other’s feces, and discovered that the microbes typically present in the higher-risk group transferred to the lower-risk group. The microbiome associated with autism susceptibility was dominant, and the previously protected strain became unprotected following the transfer. Medscape
When researchers blocked IL-17a in pregnant mice from the higher-risk group, their offspring developed normally. This demonstrated that it was not the bacteria themselves acting directly on the brain, but rather their influence on the immune molecule IL-17a — the molecular “middleman,” as Lukens described it — that carried the risk.
Critically, Lukens emphasized that this work links the immune system with neurodevelopmental disorders but in no way suggests that vaccines are contributing to autism. “There’s a definite link between the immune response and the developing brain,” he said. “It just doesn’t have anything to do with vaccines. It’s much, much earlier.” University of Virginia News
The Promise — and the Caution — of Intervention
The research opens the door to potential interventions that are relatively accessible. The microbiome can be modified through diet, probiotic supplements, or fecal transplant, all of which seek to restore healthy equilibrium among the different microorganisms that live in the gut. ScienceDaily The possibility that something as manageable as adjusting a pregnant woman’s nutrition or gut health could reduce autism risk is a significant and hopeful development.
However, the researchers are measured in their optimism. While blocking IL-17a directly might seem like a more targeted solution, Lukens cautioned that this path carries significant risk. “If you think about pregnancy, the body is basically accepting foreign tissue, which is a baby,” he said. “Maintenance of embryonic health demands a complex balance of immune regulation, so people tend to shy away from manipulating the immune system during pregnancy.” Blocking IL-17a, he added, could make the mother susceptible to a range of infections, since the molecule plays an important protective role against fungal pathogens. University of Virginia News
Lukens noted that dietary interventions, such as maintaining a balanced diet and taking Vitamin D, could potentially move forward more quickly as areas of practical exploration. Newsweek
A Broader Picture: Genetics, Inflammation, and the Developing Brain
The UVA findings do not exist in isolation. They fit within a rapidly expanding body of research seeking to understand autism’s complex, multi-layered origins.
A large study by researchers at Columbia University and the Norwegian National Institute of Public Health identified molecular signatures of gestational inflammation linked to autism risk, finding immune signatures in mid-pregnancy blood samples from mothers and in umbilical cord blood from children later diagnosed with autism that correlate with responses to infection and brain development. Columbia University Mailman School of Public Health That work aligns neatly with the UVA findings, suggesting that prenatal immune activation — regardless of its specific trigger — may be a consistent thread running through a subset of autism cases.
On the genetic side, a groundbreaking UCLA-led study published as part of the NIH’s PsychENCODE consortium identified specific transcription factor networks that drive molecular changes in the brains of people with autism spectrum disorder — marking the first time that a potential mechanism connects changes occurring in the brain in ASD directly to its underlying genetic causes. UCLA BSCRC Together, these parallel lines of research underscore that autism is not the product of a single cause, but rather an intersection of genetic predisposition, immune dynamics, and environmental context — some of which begins in the womb, shaped by factors as intimate as what a mother eats.
What Comes Next
For the next phase of research, Lukens and his team plan to investigate the potential role of other immune molecules in the development of autism and related conditions, acknowledging that IL-17a may be just one piece in a much larger puzzle. University of Virginia News
The most immediate priority, he says, is translating these mouse-model findings to human populations. “In terms of translating our work to humans, I think the next big step would be to identify features of the microbiome in pregnant mothers that correlate with autism risk,” Lukens said. “The really important thing is to figure out what kind of things can be used to modulate the microbiome in the mother as effectively and safely as we can.” ScienceDaily
For the millions of families navigating the realities of autism spectrum disorder, this research represents something meaningful: a new direction — one measured not in dramatic cures, but in the quieter, more achievable science of understanding what happens in the womb, and whether what a mother carries inside her can shape the mind growing within her.