Inflammatory lesions of the human placenta. III. The histopathology of villitis of unknown aetiology.

All placentae delivered in a large obstetrics hospital in a two-year period were examined macroscopically and histologically. Of 7505 consecutive singleton placentae, chronic focal placental villitis of unknown aetiology (VUE) was found in 575 (7.6 per cent). The clinical correlates of these cases have been published previously (Russell, 1979). The present report details histological spectra of severity and distribution of the lesions, cell types within the inflammatory foci and secondary changes consequent upon local reduction in both maternal and fetal blood flow through the placenta. Histological findings tend to support direct extension of the infection from uterine sources rather than haematogenous inoculation of the placenta. The clinical sequelae for the infant appear to correlate positively with the severity of the villitis process.