AimThis study aimed to assess the efficacy of the endometrial receptivity array (ERA) as a diagnostic tool and the impact of personalized embryo transfer (pET) for the treatment of patients with recurrent implantation failure (RIF) in Japan.MethodsFifty patients with a history of RIF with frozen‐thawed blastocyst transfers were recruited from July, 2015 to April, 2016. Endometrial sampling for the ERA and histological dating and a pET according to the ERA were performed. The receptive (R) or non‐receptive (NR) status of the endometrium as a result of the first ERA, endometrial dating, and pregnancy rates after the pET were analyzed.ResultsOf the patients with RIF, 12 (24%) were NR. Among them, eight (66.7%) were prereceptive. A clinical follow‐up was possible in 44 patients who underwent the pET. The pregnancy rates were 58.8% per patient and 35.3% per first pET in the R patients and 50.0% per patient and 50.0% per first pET in the NR patients. Discrepancies between the ERA results and histological dating were seen more in the NR patients than in the R patients.ConclusionsFor patients with unexplained RIF, there is a significance in searching for their personal window of implantation (WOI) using the ERA, considering the percentage of those who were NR and the pregnancy rates that resulted from the pET. By transferring euploid embryos in a personal WOI, much better pregnancy rates are expected.

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There have been 60 births after transplantation of cryopreserved ovarian tissue: 58 using the slow freezing method, and two using the vitrification method. DMSO and EG are widely used as cryoprotectants. However DMSO is a known epimutagen, and EG has been reported to be toxic in high concentrations. In this study, we measured residual DMSO and EG in ovarian tissue after vitrification and slow freezing. Cryoprotectants remained at a high concentration in the vitrified/warmed ovarian tissue just before transplantation (DMSO: 9.8 mg/g, EG: 9.8 mg/g). We must consider the impact of the cryoprotectants on the mother and the baby.