Long-term reproducibility and clinical utility of endometrial receptivity analysis in guiding personalized embryo transfer: case reports of sustained success over four years post-endometrial biopsy.

Aims: To demonstrate the long-term stability and clinical utility of endometrial receptivity analysis (ERA) test in guiding personalized embryo transfer (pET) for patients with a history of recurrent implantation failure (RIF), even after an intervening live birth. Methods: Two RIF patients, who had previously achieved a live birth via ERA-guided pET, sought a second pregnancy. For their subsequent personalized frozen-thawed embryo transfer cycles, progesterone administration timing was adjusted based on the receptive window identified by a single ERA test conducted more than four years earlier. No repeat endometrial biopsy was performed in either patient. Results: Both patients underwent pET following the recommendations derived from their original ERA results. Both achieved successful clinical pregnancies and subsequently delivered healthy live infants. Conclusion: These findings preliminarily suggest that repeat endometrial biopsy might not be necessary for subsequent pET in RIF patients with similar clinical backgrounds. However, given the small sample size of this case series, further large prospective studies are still needed to confirm the long-term utility of initial ERA results and the appropriateness of omitting repeat biopsies.