[Placental villitis].

Placental villitis, which is defined by the presence of lymphocytic or macrophagic inflammatory cells within the villosities, constitutes a recently-described histopathological entity. This condition is the consequence of an immune response of the feto-placental unit towards a non-specific, multiple aggression and the incidence is very low. The extent of the inflammatory reaction may culminate in placentitis, resulting in miscarriage. Although a large number of infecting agents are known to be responsible for the pathogenesis of villitis, in most cases the etiology remains unknown. The hypothesis of a failure of the mechanisms of immunotolerance during pregnancy is suggested by many authors to explain their origin.