Redefining chronic endometritis: the importance of endometrial stromal changes

OBJECTIVE: To develop diagnostic criteria for chronic endometritis and compare the prevalence of chronic endometritis between women with recurrent pregnancy loss (RPL) and controls. DESIGN: Cohort study. SETTING: Single academic fertility center. PATIENTS: Women with unexplained RPL (two or more pregnancy losses) and prospectively recruited controls without a history of RPL or infertility. INTERVENTIONS: Endometrial samples were stained with hematoxylin and eosin and CD138. A pathologist blinded to patient history recorded the number of plasma cells per 10 high-power fields (HPFs). In addition, the presence or absence of endometrial stromal changes was documented. MAIN OUTCOME MEASURE: Prevalence of chronic endometritis. RESULTS: Endometrial samples from 50 women with unexplained RPL and 26 controls were evaluated. When chronic endometritis was defined as the presence of one or more plasma cells per 10 HPFs, 31% of controls and 56% of women with RPL met the criterion. When both endometrial stromal changes and plasma cells were required for a diagnosis of chronic endometritis, no controls and 30% of women with RPL met the criteria. CONCLUSIONS: Although rare plasma cells were found in biopsy samples from controls, the presence of both plasma cells and endometrial stromal changes was limited to the RPL cohort. We propose that chronic endometritis be defined as the presence of one or more plasma cells per 10 HPFs in the setting of endometrial stromal changes. With the use of these strict diagnostic criteria, women with RPL have a significantly higher rate of chronic endometritis, supporting an association between chronic endometritis and RPL.