Comparison of clinical outcome between day 5 and day 6 single blastocyst transfers in cycles undergoing preimplantation genetic testing for aneuploidy.

OBJECTIVE: In vitro fertilization (IVF) treatment has gradually adopted the practice of culturing embryos until the blastocyst stage on the D5 or D6 as the standard approach. PGT-A is commonly used in vitro fertilization (IVF). This study aimed to evaluate the clinical outcomes of frozen embryo transfers (FETs) using single blastocyst transfers (SBTs) on the fifth (D5) or sixth (D6) day of development in cycles that underwent preimplantation genetic testing for aneuploidy (PGT-A). MATERIALS AND METHODS: The patients who had at least one euploid or mosaic blastocyst of good quality determined by PGT-A results and received single embryo transfer (SET) cycles were included in the study. In this study, the live birth rate (LBR) and neonatal outcomes were compared after the transfer of single biopsied D5 and D6 blastocysts in frozen embryo transfer (FET) cycles. RESULTS: A total of 527 frozen-thawed blastocyst transfer (FET) cycles (8449 biopsied embryos were analyzed). No significant difference in the implantation rate (IR), clinical pregnancy rate (CPR), and live birth rate (LBR) between the transfers of D5 and D6 blastocysts. Birth weight was the only perinatal outcome that showed a significant difference between the D5 and D6 groups. CONCLUSION: The study confirmed that the transfer of a single euploid or mosaic blastocyst, regardless of whether it was on the fifth (D5) or sixth (D6) day of development, can lead to promising clinical results.

Blastocyst Morphology Based on Uniform Time-Point Assessments is Correlated With Mosaic Levels in Embryos.

Avoiding aneuploid embryo transfers has been shown to improve pregnancy outcomes in patients with implantation failure and pregnancy loss. This retrospective cohort study aims to analyze the correlation of time-lapse (TL)-based variables and numeric blastocyst morphological scores (TLBMSs) with different mosaic levels. In total, 918 biopsied blastocysts with time-lapse assessments at a uniform time-point were subjected to next-generation sequencing-based preimplantation genetic testing for aneuploidy. In consideration of patient- and cycle-related confounding factors, all redefined blastocyst morphology components of low-grade blastocysts, that is, expansion levels (odds ratio [OR] = 0.388, 95% confidence interval [CI] = 0.217-0.695; OR = 0.328, 95% CI = 0.181-0.596; OR = 0.343, 95% CI = 0.179-0.657), inner cell mass grades (OR = 0.563, 95% CI = 0.333-0.962; OR = 0.35, 95% CI = 0.211-0.58; OR = 0.497, 95% CI = 0.274-0.9), and trophectoderm grades (OR = 0.29, 95% CI = 0.178-0.473; OR = 0.242, 95% CI = 0.143-0.411; OR = 0.3, 95% CI = 0.162-0.554), were less correlated with mosaic levels ≤20%, <50%, and ≤80% as compared with those of top-grade blastocysts (p < 0.05). After converting blastocyst morphology grades into scores, high TLBMSs were associated with greater probabilities of mosaic levels ≤20% (OR = 1.326, 95% CI = 1.187-1.481), <50% (OR = 1.425, 95% CI = 1.262-1.608), and ≤80% (OR = 1.351, 95% CI = 1.186-1.539) (p < 0.001). The prediction abilities of TLBMSs were similar for mosaic levels ≤20% (AUC = 0.604, 95% CI = 0.565-0.642), <50% (AUC = 0.634, 95% CI = 0.598-0.671), and ≤80% (AUC = 0.617, 95% CI = 0.576-0.658). In conclusion, detailed evaluation with TL monitoring at the specific time window reveals that redefined blastocyst morphology components and converted numeric TLBMSs are significantly correlated with all of the threshold levels of mosaicism. However, the performance of TLBMSs to differentiate blastocysts with aberrant ploidy risk remains perfectible.