Maternal immune activation (MIA), characterized by increased circulating inflammatory mediators during pregnancy, is associated with adverse pregnancy outcomes and neurodevelopmental deficits in offspring. These health outcomes often manifest differently depending on fetal-placental sex. A well-established model of MIA involves administration of a viral mimetic, polyinosinic:polycytidilic acid (PolyI:C), to pregnant rodents. Placental responses to PolyI:C contribute to the detrimental effects of MIA on offspring, but these responses have not yet been well characterized. In the present study, we profiled acute gene expression changes in male and female placentas following PolyI:C administration to pregnant rats during late gestation.