CLINICAL VALUE OF HISTOLOGIC ENDOMETRIAL DATING IN WOMEN WITH INADEQUATE ENDOMETRIUM DURING FROZEN-THAWED BLASTOCYST- STAGE EMBRYO TRANSFER: A RETROSPECTIVE PILOT STUDY

Abstract

Inadequate endometrium (IE) in preparation for a frozen embryo transfer (FET) is a challenging occurrence in assisted reproduction. While there is no accepted consensus on how to define IE a conservative approach is a measurement of less than or equal to 8mm. When the endometrium is inadequate, patients and physicians face a decision of whether to proceed with the embryo transfer. A recent study evaluating the impact of IE on FET reported a decline in pregnancy and live birth rates with each millimeter decline in endometrial thickness below 7mm (1). Histologic examination of the endometrium has been used to determine the adequacy of endometrial proliferation. To potentially reduce cycle cancellation, we evaluated the pregnancy outcome of FET cycles from patients with IE but “in-phase” histologic endometrial dating. This is a retrospective pilot study of patients between the years of 2014 and 2020 who underwent a standard hormonal endometrial preparation for FET that had been canceled due to IE defined as a maximum thickness ≤ 8mm following up to 35 days of estradiol supplementation. Endometrial biopsy was performed for histologic dating using the criteria of Noyes et al after 9 to 11 days of progesterone supplementation. Patient outcomes were also stratified based on the number and quality of embryos transferred. All study patients were determined to have “in-phase” endometrium who underwent FET cycle with the transfer of at least one good-quality blastocyst. Descriptive statistics and Pearson Correlation was calculated using SPSS software v23. A total of 21 women mean age was 38.2 ± 6.7 years and IE underwent an endometrial biopsy after estradiol proliferation and 9-11 days of progesterone supplementation. The mean endometrial thickness was 6.4 ± 0.5 mm. Seventeen women (81%) demonstrated endometria that were “in-phase” and underwent a subsequent FET cycle. The mean number of embryos transferred was 1.47 ± 0.6, the clinical pregnancy rate was 47% (8/17); miscarriage rate was 11.8% (2/17); and the live birth rate was 35.3% (6/17). There was no correlation between age and endometrial thickness (Pearson Correlation Coefficient R = 0.08, P = 0.7). Histologic dating in women with a prior canceled FET due to IE is a potentially reliable method to allow the opportunity for a successful FET with comparable outcomes to the National Average (SART National Summary Report for 2018). Studies with a larger sample size are necessary to corroborate this finding.