Clinical pregnancy outcomes in young women with diminished ovarian reserve undergoing frozen embryo transfer: a comprehensive analysis with exploratory insights into endometrial aging.

INTRODUCTION

This study compared pregnancy outcomes after frozen-thawed embryo transfer (FET) in infertile women aged <40 years with diminished ovarian reserve (DOR) versus normal ovarian reserve (NOR), incorporating exploratory analysis of potential endometrial aging factors.

METHODS

In this retrospective study, we analyzed the data of 1,362 patients aged <40 years who underwent FET between January and December 2024. Patients were categorized into two groups: the DOR (anti-Müllerian hormone [AMH] < 1.1 ng/mL, n = 136) and NOR (AMH ≥ 1.1 ng/mL, n = 1,226) groups. Pregnancy outcomes were compared after adjusting for confounding factors using inverse probability weighting. Additionally, exploratory immunohistochemical analysis of p16 expression was performed using endometrial samples from 16 patients (n = 8 per group).

RESULTS

After weighting, the clinical pregnancy rate was significantly lower in the DOR group than in the NOR group (47.0% vs. 58.3%, P = 0.040; odds ratio = 0.63, 95% confidence interval: 0.41-0.98). Exploratory analysis revealed that the expression of p16 was significantly higher in the endometrial cells of patients with DOR than in those of patients in the NOR group (P < 0.001). Furthermore, a trend toward lower clinical pregnancy rates was observed with higher p16 expression.

CONCLUSION

These exploratory findings suggest that reduced pregnancy rates in young women with DOR may involve endometrial aging mechanisms; however, the preliminary nature and limited sample size for molecular analysis necessitate cautious interpretation and warrant validation in larger and well-controlled cohorts.