Chronic endometritis and its association with implantation history, BCL6, and ERA in infertility patients

To compare the prevalence of chronic endometritis (CE) in patients with and without a history of implantation failure and to assess whether CE is associated with BCL6 overexpression or a nonreceptive endometrial receptivity analysis (ERA).

Retrospective cohort study of infertility patients at the University of California, San Francisco (01/2019-12/2024) who underwent evaluation for CE. Endometrial biopsies were performed in the luteal phase. CE was diagnosed by CD138 immunostaining performed by a single third-party laboratory (ReceptivaDx™). Concurrent BCL6 (ReceptivaDx™) and ERA® (Igenomix) results from the same tissue were analyzed when performed. CE prevalence was compared based on implantation history, and associations with BCL6 and ERA findings were evaluated.

A total of 314 patients underwent endometrial sampling for CE evaluation; 43 were excluded due to prior antibiotic exposure. Of the 271 biopsies analyzed, CE was diagnosed in 7.4% (20/271) of cases, with no significant difference between those with and without prior implantation failure (7.9% vs. 6.3%; p = 0.645). Among patients with concurrent BCL6 testing, overexpression was identified in 45.0% of the CE group and 41.9% of the non-CE group (p = 0.789). ERA results were available for 158 patients; nonreceptive endometrium was observed in 20.0% of those with CE and 18.9% in those without (p = 0.933).

CE was uncommon in patients with infertility and not more prevalent in those with prior implantation failure. CE diagnosis was not associated with BCL6 overexpression or nonreceptive ERA. Routine CE evaluation in the context of failed embryo transfer may contribute to unnecessary interventions.