Recent studies suggest that autism is often associated with dysregulated immune responses and altered microbiota composition. This has led to growing speculation about potential roles for hyperactive immune responses and the microbiome in autism. Yet how inflammation or other environmental stressors may contribute to neurodevelopmental disorders currently remains poorly understood. In a study from our lab, we identified critical roles for prenatal microbiota composition in the development of behavioral abnormalities in a murine maternal immune activation (MIA) model of autism. We show that preconception microbiota transplantation can transfer susceptibility to MIA-associated neurodevelopmental disease and that this is associated with modulation of the maternal immune response. Furthermore, we find that ablation of IL-17a signaling provides protection against the development of neurodevelopmental abnormalities in MIA offspring. Our findings suggest that microbiota landscape can influence MIA-induced neurodevelopmental disease pathogenesis and that this occurs as a result of microflora-associated calibration of gestational IL-17a responses.