Day 3 embryo morphology are critical predictors for euploid blastocyst

Abstract Purpose: To determine whether day 3 or day 1 embryo morphologic grading affected euploid blastocyst rate in PGT cycle.Methods: 2001 embryos were obtained from 219 patients in our IVF center. Embryo morphologic grading dates were collected on day 1 and day 3 respectively. Blastocyst trophectoderm biopsy were considered on day 5 or day 6 and then applied biopsies for aneuploid screening on NGS platform. Chi-square test, Student's t-tests and Mann-Whitney U tests were used to compare categorical and continuous variables between the cohorts, respectively. Logistic regressions analysis for euploidy were constructed to determine the influence of embryo morphological grading on blastocyst euploidy.Results: 811 blastocysts were able to biopsy and all the biopsies were successfully amplified for aneuploidy screening. Day 1 pronuclear pattern shown weak association with euploid blastocyst (P＞0.05). Day 3 cleavage-stage embryo scoring, including blastomere number (P＞0.01, OR=1.156), symmetry (P＞0.01, OR=0.710) and fragmentation (P＞0.01, OR=0.624) shown association with euploid blastocyst. 8 cells or ≥12 cells embryo obtained highest euploidy rate and Increasing blastomere size difference and fragmentation decreased euploidy rate .Conclusion(s): Day 3, but not day 1 embryo morphology were suitable predictors for euploid blastocyst. Day 3 morphology provides individualized, visualized and prognostic information about euploid blastocyst. Blastomere number are given properties when selecting day 3 embryo for implantation or blastocyst culturing. So, day 3 embryo Morphology provides guiding for selecting euploid embryo and improving IVF outcomes.