P-538 The association between Clinical Pregnancy Rate in IVF-Cycles and Endometrial Receptivity based on a Novel Ultrasonographic Endometrial Receptivity Scoring System
Authors: Singh M , Singh R 
Published: June 2023

Abstract

Study question
Our study was aimed towards determining whether Ultrasound based assessment of Endometrial features like blood flow, echopattern and thickness, can correlate with IVF pregnancy rates.

Summary answer
It was found that Clinical Pregnancy Rate in IVF cycles improved as the Ultrasound based Endometrial Receptivity Score increased.

What is known already
Establishing a successful pregnancy depends on the endometrium and embryo. Suboptimal endometrial receptivity account for one-third of implantation failures. Despite the in-depth understanding of the processes associated with embryo-endometrial crosstalk, little progress has been achieved for diagnosis and treatments for suboptimal endometrial receptivity. Continuously mature embryo laboratory operation technology and embryo culture technology have significantly improved the quality of embryos. In addition, because of its accuracy and non-invasiveness, transvaginal ultrasound is widely used in the field of assisted reproduction, not only for monitoring follicles, but also for evaluating endometrial receptivity and this technique can help in achieving improved pregnancy rates.

Study design, size, duration
This was a prospective study carried out from 2020 to 2022 in which 275 participants were recruited. Exclusion Criteria were the following: congenital uterine anomalies or acquired uterine diseases, submucosal myoma, intrauterine adhesion, uterine effusion and adenomyosis, hydrosalpinx; endometriosis; pre-implantation genetic test cycles, freeze-thaw embryo transfer cycles which all transferred embryos were non-high quality embryos. That is to say, FET cycles with the transfer of at least one high-quality embryo were included in the analysis.
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Participants/materials, setting, methods
275 patients underfoing FET cycle were included in this prospective study carried out from January 2020 to December 2022. Endometrial preparation protocols included natural ovulatory cycles, ovulation induction cycles, and hormone replacement treatment cycles. Transvaginal ultrasound monitoring of endometrial thickness and the diameter of the dominant follicle began on the 10-12th day of menstrual cycle. Embryo transfer was timed accordingly and frozen embryo transfer carried out.

Main results and the role of chance
A total number of 275 patients of FET were analyzed. It was found that only the echo of the endometrial central line was different between the pregnant group and non-pregnant group. Other parameters, such as endometrial thickness, volume, endometrial peristalsis, or the endometrial blood flow were not statistically different between the two groups. Then, according to the relationship between the different groups and the clinical pregnancy rate, a score of 0 to 2 was respectively scored. The sum of the scores for the six items was the patient’s endometrial receptivity score. It showed that the clinical pregnancy rate increased as the endometrial receptivity score increased, and when the receptivity score reaches at least 5, the clinical pregnancy rate is significantly improved (58.2% versus 40.4%, P = 0.001). The echogenicity of the endometrial functional layer in the pregnancy group was more homogeneous, but it did not reach statistical significance. Other parameters, such as endometrial thickness, volume, the presence or absence of endometrial peristalsis, the direction of endometrial peristalsis, or the endometrial blood flow were not statistically different between the two groups.

Limitations, reasons for caution
In the absence of data of live birth rate, we considered clinical pregnancy rate as a proxy outcome to confirm receptive endometrium. Moreover, the sample size of the study was relatively small, and it is necessary to further expand the sample size to verify our conclusions.

Wider implications of the findings
We developed an endometrial receptivity scoring system and demonstrated its validity. It may aid clinicians in choosing the useful marker in clinical practice and for informing further research. As Ultrasonography is a simple and non-invasive diagnostic tool, the cost of the IVF cycle will also reduce.

Trial registration number
NOT REQUIRED