P-336 Progesterone receptor is not downregulated in the endometrial epithelial compartment of women without embryo implantation during frozen thawed embryo transfer cycles

Abstract

Abstract Study question Is the mean endometrial progesterone receptor (PGR) expression in the endometrial epithelial compartment different between women with and without embryo implantation failure? Summary answer PGR expression is higher in epithelial endometrial compartment of women with embryo implantation failure, during mock hormonal endometrial preparation preceding frozen thawed embryo transfer cycles. What is known already PGR downregulation is critical for embryo implantation. Downregulation takes place during the window of implantation in the EEC, while, in stromal cells, it is highly expressed. Embryos are unable to attach to the maternal surface when PGR expression remains expressed in epithelial endometrial compartment (EEC). Limited information is available whether PGR is downregulated during hormonal endometrial preparation for frozen thawed embryo transfer cycles. Study design, size, duration In this cohort study, 47 endometrial biopsies were obtained between 2016-2017 Participants/materials, setting, methods Infertile women (n = 47) submitted to frozen thawed embryo transfer (FET) cycles had an endometrial biopsy after 5 days of intravaginal progesterone supplementation during mock hormonal endometrial preparation (HEP) preceding FET and prospectively followed until confirmation of an intrauterine pregnancy. PGR immunostaining was performed using standard immunohistochemical technique (clone BSB2 - BS2126, BIO SB). PRG expression was quantified using the histologic score (HScore, range from 0 - 4). Ethical approval was obtained from local ethical committee. Main results and the role of chance Age, body mass index, endometrial thickness, and the number of embryos transferred were not significantly different between women who became or not pregnant. PGR Hscore (mean ± SD) in EEC was significantly lower in pregnant women (1.2 ± 0.8; n = 14 ) compared to women without pregnancy (2.8 ± 0.6; n = 33 ) Student t-test p < 0.0001. The AUC was 0.90 ± 0.05 (95% CI: 0.7-1) p < 0.0001 displaying 94.2 % sensitivity and 80.4% specificity for a 1.65 PGR cut-off value. Limitations, reasons for caution This is an observational study to determine if a difference in PGR expression was identified in these cases Wider implications of the findings The mean PGR expression is abnormally higher in EEC of women with embryo implantation failure using HEP for FET cycles. The 1.65 cut-off may be used in future studies to investigate whether high PGR expression is a risk factor for failure of blastocyst implantation in HEP for FET. Trial registration number not applicable