The growing body of evidence associates infections during pregnancy and other inflammatory insults with developing neurodevelopmental and neurodevelopmental disorders in children, especially autism spectrum disorder. We review the specific roles that maternal immune activation (MIA) plays in the pathogenesis of autism, the critical cytokines involved, epigenetic factors, maternal antibodies and gender bias, and how MIA affects fetal neurodevelopment in the immune and neurological pathways. A comprehensive understanding of the profound impact of MIA on fetal neurodevelopment is vital for developing diagnostic criteria and medical measures for high-risk maternity and the development of treatments for multiple offspring neurodevelopmental disorders caused by maternal inflammation.