P-303 Outcomes of day 5 versus day 6 blastocysts: correlation of euploidy, implantation and embryo quality

Abstract Study question Are outcomes of day 5 (D5) blastocysts better than 6 (D6) in a PGT-A program? Summary answer Outcomes embryos show more blastocysts, quality, euploidy due to quality and higher implantation on same 6. What is known already Human optimally reach the blastocyst stage after five days culture, but some have slower development. The superiority compared fresh cycle transfers was previously demonstrated attributed mainly endometrial asynchrony. Data from frozen showed conflicting results, studies announced pregnancy rates transfer with transfer, while others shown equivalent outcomes. However, none these between euploid versus those (D6). design, size, duration Retrospective observational study performed private centre May 2017 December 2022. includes data analysis 5599 D5 D6 undergoing obtained 819 patients following 1295 PGS cycles. 948 outcome were transferred 789 embryo transfers. Blastocyst morphology scored 3 groups: A: excellent (AA, AB, BA), B: good (BB), C: average poor-quality (BC, CB, CC). (Gardner-Schoolcraft classification) Participants/materials, setting, methods NGS technology offered advanced maternal age and/or repeated IVF failures. Trophectoderm biopsies embryos, laser assistance. (Navilase, OCTAX) We both populations (D5 D6) terms number achieved distribution each population. As primary outcome, same-quality group results rate according development D6). Main role chance Vast majority biopsied (71.8%, n = 4017) (28.2%, 1582) D6. proportion three quality-categories D5/D6 uneven. Quality A 18.6% vs 3,5%. B 72,4% 59,6%. C 9,0% 36,9%, respectively, showing significative differences (Chi^2 p-values groups< 0.001), concluding that overall Overall population 31,3% 23,3% (p value <0.001), significant difference favour D5. But layering categories D5/D6, 44,7% 51,8% for A, 29,6% 26,6% 17,6% 14,9% C, no p-values: 0,331; 0,067; 0,280). Euploidy not dependant dependant. (65,9%) (40,4%) <0.001). Layering again, 75,0% 66,7% 63,8% 46,4% 35,3% 26,3% respectively. Despite being all groups only shows differences. 0,651; < 0.001; 0,360). Implantation Limitations, reasons caution limited by its retrospective nature low grade D6-euploid available transfer. Additionally, it common one increase chances pregnancy, losing track type. Wider implications findings It uncontested had reproductive potential, we managed quantify this potential based which remains most important predictive biomarker selecting best reducing time achieve pregnancy. Trial registration applicable