Antibiotic cured chronic endometritis remains a risk factor for early pregnancy loss in the subsequent frozen euploid embryo transfer

Research question: Do patients with antibiotic-cured chronic endometritis (CCE) have a comparable pregnancy outcome to those with non-chronic endometritis (NCE) in the subsequent frozen embryo transfer (FET) cycle?Design: A retrospective cohort analysis included 833 patients in their first FET cycles with single euploid embryo transfer. Chronic endometritis (>5 CD138+ plasma cells per high-power field [CD138+/HPF]) was treated with standard antibiotic therapy. Patients were classified into two groups: the NCE group (n = 611, <5 CD138+/HPF) and the CCE group (n = 222, >5 CD138+/HPF and cured after antibiotic treatment). Pregnancy outcomes were compared. NCE group was divided into subgroup 1 (CD138+/HPF = 0) and subgroup 2 (CD138+/HPF =1-4) for further analysis. Results: The rate of early pregnancy loss (EPL), incorporating all losses before 10 weeks' gestation, was significantly higher in the CCE group than the NCE group (21.2% versus 14.2%, P = 0.016), and the difference was statistically significant (adjusted odds ratio [AOR] 1.68, 95% confidence interval [CI] 1.11-2.55). No significant differences were observed between the two groups with regard to other pregnancy outcomes. In the subgroup analysis, the EPL rate and biochemical pregnancy rate were significantly higher in subgroup 2 than subgroup 1(17.2% versus 9.4%, AOR 2.21, 95% CI 1.30-3.74; 12.2% versus 6.9%, AOR 2.01, 95% CI 1.09-3.68). Conclusions: Chronic endometritis cured by standard antibiotic therapy remains a risk factor for EPL in FET cycles, although no differences were found in live birth rates between patients with CCE or with NCE.