Retained pregnancy tissue after miscarriage is associated with high rate of chronic endometritis

The objective of this study was to evaluate prevalence of chronic endometritis in a cohort of patients with retained pregnancy tissue (RPT) following miscarriage, with and without a history of recurrent pregnancy loss (RPL). In a cohort of our single academic fertility centre, we evaluated women with unexplained RPL (two or more losses) without evidence of RPT and women undergoing hysteroscopic resection of RPT following miscarriage. Endometrial samples underwent staining with H and E and CD138. A pathologist blinded to patient history recorded the number of plasma cells per 10 high power fields (HPF) and the presence or absence of endometrial stromal changes. Our main outcome measure was to measure the prevalence of chronic endometritis. Endometrial samples from 50 women with RPT following miscarriage and 50 women with unexplained RPL without evidence of RPT were reviewed. The prevalence of chronic endometritis was significantly higher in the RPT cohort (62% versus 30%). A multivariable regression demonstrated significantly higher odds of chronic endometritis in the RPT cohort, aOR 7.3 (95% CI 2.1, 25.5). We conclude that women with RPT following pregnancy loss have a high rate of chronic endometritis, suggesting that RPT is a risk factor for this disorder. Impact StatementWhat is already known on this subject? Known risk factors for chronic endometritis include a history of pelvic inflammatory disease, intrauterine polyps and fibroids. The aetiology for increased chronic endometritis among women with RPL is unknown.What do the results of this study add? The prevalence of chronic endometritis is significantly higher among women with retained pregnancy tissue (RPT) following miscarriage compared to women with RPL. These data presented suggest that RPT is associated with chronic endometritis among women with a history of miscarriage.What are the implications of these findings for clinical practice and/or further research? We suggest a pathologic evaluation for chronic endometritis be performed on all patients who undergo hysteroscopic resection of RPT following miscarriage. Our findings also suggest that a uterine cavity evaluation with hysteroscopy to evaluate for RPT may be reasonable in women with a history of miscarriage who are found to have chronic endometritis on endometrial biopsy. Further research is needed to determine if resection of retained tissue is sufficient to treat RPOC associated chronic endometritis, or if additional antibiotic treatment is necessary.