Association Between Morphologic Grading and Implantation Rate of Euploid Blastocyst

Abstract Objective: To determine the association between the morphologic grading and implantation rate of euploid blastocysts in single frozen-thawed embryo transfer (SET) cycles.Design: Retrospective cohort study.Setting: Single university-based fertility centerPatient(s): Women aged 20–40 years undergoing euploid SET from January 2017 to December 2019 were identified. Main Outcomes Measure(s): Implantation rate (IR) Result(s): A total of 271 euploid SET cycles were included. The cycles were divided into three groups based on their morphologic grading before cryopreservation: good-quality (n = 58), average-quality (n = 88) and poor-quality blastocysts (n = 125). Good-quality blastocysts yielded statistically significantly higher implantation rates than poor-quality embryos (79.31% vs. 48%; P＜0.001). Planned subgroup analyses by age and the day of TE biopsy were conducted. Logistic regression analyses that adjusted for these variables identified higher implantation rates (adjusted odds ratio(aOR)= 4.083, 95% confidence interval (CI):1.836–9.082, P＜0.001) for the good-quality blastocysts than for those that underwent poor-quality cycles in women aged <35 years, but not in women aged ≥35 years (aOR=6.074, 95%CI: 0.456-80.919, P=0.172). The implantation rates were higher among women with good-quality blastocysts on both Day 5 and Day 6 of TE biopsy than among those with poor-quality blastocysts (Day 5, aOR=3.294, 95%CI:1.260-8.616, P = 0.015; Day 6, aOR=4.179, 95%CI:1.004~17.399, P=0.049). Day 5 euploid blastocysts had no significant difference in implantation potential and early spontaneous abortion rate compared with similarly graded Day 6 euploid blastocysts.Conclusions: Blastocyst morphologic grading was associated with implantation rate for euploid embryo transfers after adjustment for potential confounders. These findings suggest that evaluating blastocyst morphology is critical when selecting the best euploid blastocyst.