P-425 Premature follicular-phase progesterone increase in ART cycles and endometrial receptivity: evaluation of new, more reliable predictors

Abstract Study question Is plasma Progesterone (P) at HCG administration more sensitive in predicting endometrial receptivity in fresh IVF cycles than PFI (progesterone-follicles index) and POI (progesterone-oocytes index)? Summary answer Our data suggest that POI predicts endometrial receptivity defect better than the P assay alone, thus allowing better decision making. What is known already The premature increase in plasma P in the follicular phase of stimulated IVF cycles has been associated with a lower embryo implantation rate because of reduced endometrial receptivity. There is still no consensus on how this impediment to implantation should occur and what threshold should be used. Moreover,since the efficacy of P increase in conditioning reproductive outcomes is more intense in patients with normo- and poor-response and generally inversely proportional to the ovarian response to stimulation, PFI and POI, which better reflect the average amount of P secreted from the follicles, have been suggested as potential additional markers of receptivity. Study design, size, duration Retrospective analysis of fresh IVF-ET cycles. PFI was obtained dividing the plasma P level on the day of hCG administration by the number of follicles ≥14 mm; POI by the number of oocytes retrieved. Pearson correlations, ROC curves, multivariate logistic regression analysis and Cox regression were performed to evaluate the predictive value of PFI and POI for the main outcomes we considered: ongoing pregnancy rate (OPR) and live birth rate (LBR). Participants/materials, setting, methods Women undergoing IVF cycles at San Paolo University Hospital in Milan between 2016 and 2021 were enrolled. As exclusion criteria, we considered previous ovarian surgery, endometriosis, severe male factor and cycle interruption before the embryo transfer. We collected the following data: age of the woman; stimulation protocol; total amount of FSH administered; P and Estradiol (E2) levels and number of follicles >14 mm on induction day; number of oocytes collected; OPR and LBR. Main results and the role of chance A total of 662 fresh embryo transfers (ETs) were performed and 214 pregnancies were achieved. We observed a statistically significant difference in age, number of total embryos and POI between women who became pregnant and those who did not. Specifically, Pearson’s correlation revealed a significant positive correlation between pregnancy and number of total embryos (r = 0.165, p