Methods are presented herein for reducing the risk of developing a psychiatric disorder (e.g., autism like disorder) in a fetus involving administering an inhibitor of T helper 17 (Th17) cell activity to the mother of the fetus, while the mother is pregnant with the fetus at risk. Also encompassed herein is a method for treating a fetus in utero to reduce the risk of abnormal cortical development that arises from Th17 cell-mediated activity.
