Comparison of Doppler ultrasound indices of uterine artery and sub endometrial blood supply in frozen embryo transfer with and without repeated implantation failure: A cross-sectional study

Background: Uterine blood supply has been identified as a potential factor in implantation failure. Objective: This study aimed to investigate Doppler indices in the uterine artery, including vascular flow and resistance, as well as the amount of sub-endometrial blood supply in women with a history of repeated implantation failure (RIF) compared to the non-RIF group. Materials and Methods: This cross-sectional study was conducted with 139 women candidates for frozen embryo transfer in Yazd Reproductive Sciences Institute, Yazd, Iran from February to July 2023. Group A (n = 68) included women with a history of more than 2 RIF, and group B (n = 71) included women candidates for implantation for the first time without RIF. Doppler ultrasound indices of uterine artery and sub-endometrium, including sub-endometrial flow, uterine artery flow, uterine artery resistance, and peak systolic velocity, were recorded. Results: No significant differences were observed in uterine artery Doppler pulsatility index and peak systolic velocity between groups, but the uterine artery resistance index was significantly higher in the A group (p < 0.001). A significant difference was observed in the perfusion area between groups. 60/68 women in the group A had endometrial perfusion in areas 2 and 3 (p < 0.001). Conclusion: Our study revealed that women with RIF exhibited higher resistance index in sub-endometrial arteries compared to the non-RIF group. Key words: Doppler ultrasound, Frozen embryo transfer, Repeated implantation failure.