Naval oceanographer Carina Block had a hunch that the jet exhaust fumes she and her fellow female sailors were regularly exposed to, combined with unavoidable job stress, was leading to adverse health outcomes for their children. A new study in mice backs up Block’s suspicion, finding that air pollution along with housing insecurity while pregnant leads to autism-like social behavior and differently wired brains in male, but not female, pups. The immune system seems to be at fault.