LAUSR

Abstract Endometrial thickness (ENT) measurements are important to evaluate endometrial receptivity. The effect of endometrial thickness on pregnancy outcomes has been discussed for many years with conflicting results. The aim of our study was to find out the effect of endometrial thickness (ENT) change in response to progesterone on pregnancy outcomes in embryo transfer (ET) of fresh oocyte donation (OD) recipients. The study was designed retrospectively including 134 embryo transfers with fresh OD recipients. ENT was measured by ultrasonography (USG) on the day of initial progesterone administration (ENT1) and on ET day (ENT2). The primary outcome was to determine any correlation between the ENT change and pregnancy outcomes. ENT increased in 56.7% of cases and decreased in 43.4%. Clinical pregnancy rate (CPR) in recipients with increased ENT was 76.3%, and live birth rate (LBR) was 72.4%. CPR in recipients with decreased ENT was 69.0% and LBR was 65.5%. There was no significant difference between recipients with either increased or decreased ENT regarding CPR and LBR (p = .225 and p = .253, respectively). Our study revealed that ENT change after 6 days of progesterone administration, whether increased or decreased, does not have any significant effect on LBR and CPR in fresh OD recipients. IMPACT STATEMENT What is already known on this subject? Measurement of endometrial thickness is beneficial to determine the endometrial receptivity. However, there is controversy in the literature regarding the usefulness of measuring endometrial thickness. What do the results of this study add? To the best of our knowledge, this is the first study performed with fresh oocyte donation cycles with large number of recipients for live birth rate outcomes in the literature so far. In this study, we sought to assess the impact of endometrial thickness change, in response to 6 days of progesterone administration, on live birth rate and clinical pregnancy rate in embryo transfer of fresh oocyte donation recipients. We did not find no significant effect of endometrial thickness change on live birth rate when fresh young donor oocytes are fertilised with sperms having normal parameters, and implanted in oestrogen and progesterone primed endometrium. What are the implications of these findings for clinical practice and/or further research? Measurement of endometrial thickness in patients under infertility treatment provides little benefit to clinical outcomes.