Relevance of chronic endometritis in recurrent implantation failure and recurrent miscarriage

Background: Due to causes which frequently cannot be identified, recurrent implantation failure and recurrent miscarriages are frustrating situations for both patients and treating physicians. In addition to embryonic factors, endometrial causes are discussed as potential risk factors, with chronic endometritis (CE) coming into the focus of scientific interest in recent years. Objective: This article aims to provide an overview of the clinical symptoms, pathophysiology, diagnostics and potential treatment options of CE in recurrent implantation failure and recurrent miscarriage. Results: Studies indicate that CE has negative effects on implantation and development in (early) pregnancyvia various mechanisms (including an impact on cytokine secretion and alterations in the composition of lymphocyte subpopulations in the endometrium). The immunohistochemical detection of CD138-positive plasma cells in endometrial biopsies has been established as the gold standard for the diagnostics of CE; however, there is still no consensus on the exact diagnostic criteria causing high variations in the reported prevalence of CE in these patient groups of about 10-50%. Successful treatment is achieved with antibiotics, as evidenced both histologically by plasma cell clearance and clinically by higher implantation, pregnancy and live birth rates. Conclusion: Data on the diagnostics and treatment of CE in patients with recurrent implantation failure and recurrent miscarriage are promising. The determination of exact diagnostic criteria and the treatment of patients with a persistence of CE despite antibiotic treatment are particularly challenging. Further randomized, ideally placebocontrolled, prospective studies with adequate case numbers are needed to provide results in the coming years, so that the value of CE can be further strengthened.