The importance of measuring the endometrial cavity length in deciding the ideal place for embryo transfer: a retrospective cohort study.

BACKGROUND

The relationship between clinical pregnancy rates and embryo transfer positioning remains a matter of considerable debate, with persistent inconsistencies reported across existing studies. A notable limitation of existing studies is their failure to systematically account for anatomical variations in the endometrial cavity dimensions. The purpose of the present study was to determine the ideal location for embryo transfer according to different endometrial cavity lengths.

METHODS

This retrospective cohort study included 1237 patients who underwent frozen-thawed embryo transfer (FET). Patients were divided into two groups based on different endometrial cavity lengths (ECL): group 1 included 726 women with ECL < 32 mm, and group 2 included 581 women with ECL ≥ 32 mm. We then compared the clinical pregnancy rates according to the different air bubble-uterine fundus distances.

RESULTS

In group 1, the optimal value of air bubble-uterine fundus distance (BFD) for the highest clinical pregnancy rate was 11 mm. In group 2, the ideal BFD for the highest clinical pregnancy rate was 15 mm.

CONCLUSIONS

Our study demonstrated a clear correlation between endometrial cavity length and the ideal embryo deposition site, highlighting the importance of measuring endometrial cavity length during embryo transfer. Moreover, the relative positioning methodology that determined the ideal embryo transfer distance from the fundal endometrium to the air bubble for the highest pregnancy rate based on individual endometrial cavity length was superior.