P-464 A decrease of the zone of favorable implantation in certain forms of the uterine cavity as a cause of implantation failure in embryo transfer programs

Study question To determine the influence of the shape of the uterus and the volume of the favorable implantation zone (Z) on the effectiveness of embryo transfer. Summary answer The reason for implantation failure may be a decrease of favorable zone of implantation which needs more objective and measurable criteria What is known already The uterine cavity abnormalities could be the cause of reproductive disorders, including failure of embryo implantation in ART programs. At the same time, there is no consensus regarding the negative impact of minor changes of the uterine cavity on the embryo transfer success. If the uterus has a small notch in the bottom and slight thickening of the side walls, it can fall into the normal category. But the space in the centre of the uterine cavity with the thickest endometrium, which we call favorable implantation zone will be reduced in these cases. Study design, size, duration We retrospectively analyzed the results of transfers of genetically tested embryos between March 2018 and March 2024 in patients with preserved coronary 3D images of the uterine cavity. Participants/materials, setting, methods The 3D images of uterine cavity were obtained on the day of embryo transfer in 2184 cycles. We divided all cases depending on the volume of Z. The volume of Z was calculated automatically, taking into account the height and the width of the zone and the thickness of the endometrium. Main results and the role of chance In the first group (Z volume > 15 mm3) there were 1134 transfers, pregnancy rate (PR) was 64%, live birth rate (LBR) - 52%, in the second group (Z volume 10.1-14.9 mm3) there were 960 transfers with PR - 34% and LBR - 29%, in the third group (Z volume ˂ 10 mm3) there were only 90 transfers, PR - 13.3%, LBR - 2.2%. The difference between the groups was statistically significant. The last group had the highest percentage of early pregnancy losses (10 out of 12 pregnancies). The part of the patients with an endometrium less than 8 mm in the third group was also the largest. Limitations, reasons for caution Our data were recieved in retrospective study. The results need confirmation by prospective one. Wider implications of the findings Potential possibility to influence implantation rate in the group of patients with decreased favorable implantation zone. Trial registration number No