Improvement Of Pregnancy Outcome By Targeting A Customized Timing Of Frozen Embryo Transfer In Patients For Donor Egg Recipients.

The aim of this study was to optimize pregnancy outcome using customized embryo transfer according to the evaluation of endometrial receptivity of patients included in eggs donation program. Endometrial biopsies are performed during the implantation windows 5-9 days after progesterone administration under hormone replacement therapy. Then, the transfer strategy consists in performing cET of blastocysts according the endometrium receptivity day identified using the Win-Test. Therefore, frozen day 2/3 embryos were transferred 72/48 hours before this specific receptivity day, respectively. When the endometrial sample was defined as non-receptive, a second evaluation was performed later, according to transcriptomic result. 45 patients in eggs-donation program due to an advanced age (n=36) or premature ovarian failure (n=9) were included. RNAs from biopsies were extracted and the Win-Test gene expression was assessed by qRT-PCR. Positive pregnancy test was defined as at least two consecutive positive b-hCG serum concentration. Clinical pregnancy, implantation rate and live birth rate were recorded after cET according to the transcriptomic results. Analyses of endometrial receptivity status (n=108 biopsies) in patients in oocyte donation program (age mean ± SD: 41.2 ± 3.8 years) revealed a strong inter-patient variability of the moment of the opening of the receptivity window within the implantation window. Majority of patients (84%) present a delay of their receptivity window compared to the classical timing for blastocyst transfer (16% at Pg+5/Pg+6). This delay was mainly between 1 (40%) to 2 days (33%), or more (11%). Then, a cET can to be perform during a subsequent cycle according the endometrium receptivity day and in the respect of the synchronization of the fœto-maternal dialogue. Using this strategy, the positive b-hCG and clinical pregnancy rate per patient were 73.3% and 60%, respectively. The implantation and live birth rates after cET were 50% and 48.9%, respectively. This finding demonstrated that customized embryo transfer according to the specific cycle day where endometrium is receptive improves both implantation rate and live birth rate in patients in oocyte donation program.