Research shows the gut microbiome plays a major role in health, influencing everything from weight and mental health to autoimmune diseases. A new study in The Journal of Immunology has found a possible link between a mother’s gut microbiome and autism in offspring.

“The microbiome can shape the developing brain in multiple ways,” said John Lukens, lead researcher at the University of Virginia. “It’s really important to the calibration of how the offspring’s immune system is going to respond to an infection or injury or stress.”

The study focused on a molecule called interleukin-17a (IL-17a), known for fighting infections but also capable of influencing brain development in the womb.

In experiments, mice with gut microflora that triggered IL-17a responses gave birth to pups that developed autism-like behaviors. When IL-17a was blocked, or when healthy mice received gut bacteria from the first group, the outcome changed—showing that maternal gut health directly influenced offspring behavior.

Though early and based on animal models, the findings suggest that “the health of the mother’s gut plays at least some role” in autism risk. Researchers now aim to study human pregnancies and explore other molecules beyond IL-17a.