Uninfected but not unaffected: chronic maternal infections during pregnancy, fetal immunity, and susceptibility to postnatal infections.

Chronic infections during pregnancy are highly prevalent in some parts of the world. Infections with helminths, Trypanosoma cruzi, Plasmodium spp, and HIV might affect the development of fetal immunity and susceptibility to postnatal infections independently of in-utero transmission of the pathogens. Fetal adaptive immune responses are common in neonates who have been exposed to maternal infection during pregnancy but not infected themselves. Such responses could affect the development of immunity to the homologous pathogens and their control during the first few years of life. Fetal innate and regulatory responses might also affect immunity to unrelated pathogens and responses to vaccines. Strategies to improve child health should integrate the possible clinical implications of in-utero exposure to chronic maternal infections.