Endometrial factors and pregnancy loss frequency in recurrent pregnancy loss patients: comparing RT-PCR microbiology, microbial cultures, and immunohistochemistry of endometrium biopsy

The objective of this study is to investigate the presence of bacteria in endometrial samples from patients with recurrent pregnancy loss (RPL) and explore potential correlations between bacterial presence, chronic endometritis, and previous pregnancy loss history. Endometrial samples from 90 RPL patients were analysed using RT-PCR to detect 10 specific bacterial species. A subgroup of 65 patients underwent additional microbial culture and immunohistochemistry for plasma cell identification. Correlations between bacterial presence, chronic endometritis, and the number of previous pregnancy losses were evaluated. We detected at least one out of 10 chosen bacteria DNA by RT-PCR in 24.4% (22/90) of endometrial samples. Patients with PCR-identified bacteria had a significantly higher number of previous pregnancy losses (median 3 vs 2, p = 0.01). No correlation was observed between bacterial presence and chronic endometritis diagnosis. A significant correlation was found between bacterial detection by PCR and microbial culture (p = 0.03), though culture methods detected fewer positive cases. In RPL patients, detecting DNA from at least one of 10 selected bacterial species by RT-PCR correlates with a higher number of previous pregnancy losses. However, this bacterial presence does not correlate with chronic endometritis diagnosis based on the CD138 immunohistochemistry-identified plasma cell count. These findings suggest a potential role of endometrial bacteria in RPL that may be independent of the classical inflammatory response associated with chronic endometritis.