A pilot study of the frequency and significance of placental villitis.

The prevalence of inflammatory villous lesions was determined in a prospective study of 120 consecutive placentas. Cord blood IgM level was measured as an indicator of fetal intrauterine infection, and the birthweights of the infants were noted. Ten cases of villitis were found. Two infants had elevated cord blood IgM and one of them also had amniotic infection. As only one case of villitis had corroborative evidence of transplacental intrauterine infection, 90% of the lesions require an alternative explanation. The severity of the lesions correlated with the presence of low birthweight. The quality of the inflammatory infiltrate was also considered. Only one case included plasma cells; the remainder showed lymphohistiocytic infiltration. The case with plasmacytic infiltration was the one with elevated cord blood IgM. It is concluded that placental villitis is usually not an infective condition and its aetiology remains unknown.