TROPHECTODERM GRADE AND THE DAY OF TE BIOPSY SIGNIFICANTLY CORRELATE WITH PREGNANCY RATE IN EUPLOID BLASTOCYST TRANSFER

Abstract

Currently, PGT-A becomes popular, and euploid blastocysts are usually selected for blastocyst transfer (BT). It is obvious that the morphological evaluation using trophectoderm (TE) grade and inner cell mass (ICM) grade are important for selecting a blastocyst, but it has been now controversial which grade can more contribute to achieve pregnancy even though using euploid blastocysts. The aim of this study is to evaluate which grade is more important, TE or ICM, to predict pregnancy among the euploid blastocysts. This study was a retrospective cohort study. From 1/2020 to 3/2021, 720 BT cycles in 520 patients were recruited. All blastocysts underwent TE biopsy on Day 5 (D5) or Day 6 (D6) for PGT-A, and those were cryopreserved. The extracted TE cells were analyzed by NGS. Clinical pregnancy rate (CPR) and miscarriage rates(MR) were evaluated according to the morphological evaluation and the day of TE biopsy. Fisher's exact test and multiple logistic regression analysis were utilized as appropriate. A p-value of < 0.01 was considered statistically significant. All statical analysis were performed with EZR. The maternal age was 36.6 ± 4.7 (mean ±S.D.). The CPR using D5 blastocyst showed 65.7%, and this was significantly higher than that of D6 blastocyst (43.8%, p<0.01). According to the TE grade, the CPRs of TE-A, B, and C were 71.6%, 52.8%, and 26.2%, respectively, with significant difference. In contrast, the CPRs of ICM-A, B and C were 67.8%, 56.8%, and 32.3%, respectively, without significant difference. The CPRs of the expansion stage were also no significant difference (Table1). The MR using D5 and D6 blastocysts were 10.6% and 17.0%, without significant difference, MR using TE-A (10.5%), B (12.2%) and C (36.4%), and using ICM-A (8.6%), B (15.0%) and C (50%) showed no significant difference neither. After adjusting for cofounders, not ICM grade but TE grade well correlated with CPR, and the day of TE biopsy also could be a good predictor to achieve pregnancy. The any morphological parameters and the day of TE biopsy had no relationship with miscarriage rates. Clinicians should focus on both the TE grade and the day of TE biopsy to select a good blastocyst for BT.