Since enzymes along the kynurenine pathway (mainly IDO and KMO) are activated by pro-inflammatory cytokines (Alberati-Giani et al., 1996), the present study supports the concept that infection and/ or inflammation could influence early brain development, perhaps contributing to the established effects of infection during pregnancy on embryonic brain development (Brown, 2006, Brown, 2011, Meyer and Feldon, 2010, Hornig et al., 1999). The gene discussed is IDO1; the disease is infection.