P-480 An endometrial receptivity scoring system evaluated by ultrasonography in patients undergoing frozen-thawed embryo transfer: a prospective cohort study

Abstract Study question Can a scoring system based on ultrasound indicators evaluate the endometrial receptivity (ER) in a noninvasive and effective manner? Summary answer A noninvasive ultrasound scoring system was proposed, through which, a patient’s ER situation can be assessed in a noninvasive, efficient and accurate manner. What is known already Endometrial receptivity (ER) refers to the receptiveness of the endometrium to embryonic implantation and subsequent development. The endometrium plays a crucial role in embryo implantation, especially when the embryo quality is good. Ultrasound technology has become a routine method for ER evaluation. The independent evaluation value of various ultrasonic indicators is controversial. Some researchers designed a multi-index prediction system, but the prediction results vary. To further understand ER, we performed this prospective cohort study to help evaluate ER in a noninvasive and efficient manner. Study design, size, duration This prospective study included 197 infertile women undergoing FET from April 2019 to July 2021. Transvaginal three-dimensional ultrasound was performed on the transfer day to evaluate ER, including endometrial thickness, morphology, volume, movement, blood flow and flow index. Participants/materials, setting, methods This study was conducted at the Reproductive and Genetic Hospital of CITIC-Xiangya. The primary outcome of this study was the clinical pregnancy rate. All included patients were divided into a pregnant group and a nonpregnant group according to whether clinical pregnancy was achieved. Main results and the role of chance A total of 197 FET patients with 139 pregnancies (70.5%) were analysed. Primary infertility (adjusted odds ratio (aOR), 1.98; 95% confidence interval (CI), 1.01–3.882; P = 0.047) and more frequent endometrial peristalsis (aOR, 1.33; 95% CI, 1.028–1.722; P = 0.03) were protective factors against clinical pregnancy. Scores of 1 to 2 were given according to the relationship between different groups of ultrasonic indices and the clinical pregnancy rate (CPR). A patient’s ER score was the sum of the scores of the 6 items. The ER score was significantly higher in the pregnant group than that in the nonpregnant group (7.40 ± 1.73 versus 6.33 ± 1.99, P = 0.001). The CPR increased as the ER score increased; the CPR significantly improved for the group with total ER scores of < 6 to ≥ 6 (45.5% versus 75.6%, P = 0.001). Limitations, reasons for caution First, this study only included natural cycles of FET. The application for other populations remains to be verified. Second, perhaps with the progress of ultrasonic technology, there will be new and more direct indicators. Third, we did not further explore the relationship between ER and the live birth rate. Wider implications of the findings The scoring system provides a broader idea for guiding clinical practice to perform more efficient transplantation and provide a noninvasive evaluation of ER in the future. Trial registration number None