Researchers have found that the immune responses of a female mouse before pregnancy can predict how likely her offspring are to have behavioural deficits if the immune system is activated during pregnancy. The study results could help resolve what role serious infections during pregnancy play in the later development of conditions such as autism and schizophrenia in offspring. Both genetics and a variety of environmental risk factors are thought to play a role in mental illness. Although the risk from maternal immune activation is low, it could provide a way into the underlying problems that lead to schizophrenia or autism.