Readers of this book and blog are well aware that influenza infection during pregnancy increases the risk for schizophrenia and autism in the offspring. Now Alan Brown and colleagues at Columbia Univ expand that risk to bipolar disorder (BD). The new paper provides evidence that the risk for BD increases nearly 4-fold, with nearly a 6-fold increase for a BD subtype with psychotic features. These numbers are similar to the 3-7-fold increase for schizophrenia risk that Brown found found previously. While the most significant risk for a schizophrenia outcome was associated with infection during the first half of pregnancy (primarily late first and early second trimester; not third), the increased risk for BD in the offspring appears to be associated with infection at any time during pregnancy. There is a very slightly increased risk for infection during the 2nd or 3rd trimesters. Thus, it is possible that the timing of the infection may influence the outcome, although genetic background and the intensity of the infection could also play a role.