Placental microbiology and histology and the pathogenesis of chorioamnionitis.

The present study was undertaken to determine the proportion of cases of chorioamnionitis that was caused by microbiologic agents. Seventy-five placentas were processed to isolate aerobic and anaerobic bacteria and chlamydia. Results were correlated with the presence or absence of histologic and clinical chorioamnionitis. Bacteria were recovered from 72% (18 of 25) of placentas with histologic chorioamnionitis and from nine of 11 cases (82%) of clinical chorioamnionitis, all of which had histologic chorioamnionitis. Bacteria were recovered from only 15% (six of 39) of placentas without histologic chorioamnionitis. Nearly 50% of the bacteria recovered from placentas were anaerobes, often fastidious in their growth requirements. Often two to three such anaerobes were recovered from a placenta. Findings of the present study increase the possibility that bacteria are responsible for most cases of chorioamnionitis.