Objective:

To assess the impact of chronic endometritis (CE) detection and management on pregnancy outcomes in women experiencing first implantation failure (FIF) during frozen-thawed embryo transfer (FET) cycles.

Approach:

• Study Design: Retrospective cohort analysis of 4,528 women who experienced FIF after IVF/ICSI, with 2,885 included for analysis.
• Diagnostic Method: Participants underwent hysteroscopy-guided endometrial biopsy with CD138 immunohistochemical evaluation.
• Treatment Protocol: Women diagnosed with CE received standardized empirical antibiotic treatment followed by post-treatment CD138 reassessment.
• Outcome Measures: Primary outcome was live birth rate (LBR); secondary outcomes included clinical pregnancy rate (CPR) and early miscarriage rate (EMR).

Key Findings:

• CE was identified in 16.8% of participants, with a cure rate of 89.1% after two courses of antibiotics.
• No significant difference in pregnancy outcomes between women with CD138-positive counts of 0/HPF and 1-4/HPF.
• Women with persistent chronic endometritis (PCE) had lower LBR (28.3% vs. 41.8%) and CPR (39.6% vs. 56.6%) compared to those with CD138-positive/HPF ≤4.
• In IPTW-weighted analysis, PCE was significantly associated with lower CPR (weighted OR 0.65) and showed a trend towards lower LBR (weighted OR 0.73).

Interpretation:

An endometrial CD138-positive plasma cell count of ≤4/HPF is not associated with impaired pregnancy outcomes. PCE is linked to poorer reproductive outcomes.

Limitations:

• Observational design limits causal inference.
• Potential confounding factors may not have been fully accounted for.

Conclusion:

CE management can improve pregnancy outcomes in women with FIF, but persistent CE is associated with lower reproductive success.