#105 : Single Day 5 Versus Day 6 Euploid Blastocyst Transfer: The Impact of Embryo Quality on Pregnancy Outcomes

Abstract

Background and Aims: Selecting embryos with the highest implantation potential is crucial to in vitro fertilization (IVF) success. The day of biopsy, Day 5 (D5) or Day 6 (D6), and embryo quality have been suggested as influential factors in determining the clinical outcomes of single euploid blastocyst transfers. However, evidence supporting the superiority of D5 over D6 blastocysts remains inconclusive. This study aims to compare clinical outcomes following transfer of euploid blastocysts of varying quality biopsied on day 5 versus day 6. Methods: A retrospective cohort study was conducted at an Assisted Reproductive Center, analyzing 774 patients with Day 5 biopsies and 155 patients with Day 6 biopsies who underwent embryo transfer between January 2019 and February 2022. Results: The live birth rate was significantly lower in the euploid D6 group than in the euploid D5 group (38.71% vs. 55.04%, RR=0.70, 95% CI=0.57-0.87). The outcomes were significantly influenced by the quality of the embryos. Excellent embryos yielded live birth rates of 62.14% and 53.61% for D5 and D6 biopsies, respectively, while good embryos demonstrated live birth rates of 45.18% (D5) and 32.21% (D6). For fair embryos, the live birth rates were 28.64% (D5) and 19.32% (D6). The outcome difference was statistically significant across embryo quality categories (p<0.05). The adjusted risk ratios of clinical outcomes indicated that excellent euploid Day 5 embryos consistently outperformed other types of embryos. Conclusions: Our study supports that the biopsy day and embryo quality are crucial factors in determining the success of single euploid blastocyst transfers. Excellent euploid Day 5 transfers yielded superior outcomes, providing valuable insights for clinicians and patients when selecting embryos for transfer in IVF cycles.