Transfer the best and biopsy the rest? Blastocyst euploidy rates differ by morphology and day of biopsy

Purpose: To determine if blastocyst euploidy rates differ by embryo morphology or day of biopsy. Methods: We performed a retrospective analysis of euploidy rates based on patient age, overall embryo morphology grade (good, fair, or poor), and day of biopsy (days 5, 6, or 7) for blastocysts undergoing preimplantation genetic testing for aneuploidy (PGT-A). Our primary analysis included 904 embryos from oocytes age 33–39 years at retrieval. Results: In our primary analysis, euploidy rates were higher for good quality embryos than poor (64% vs. 48%, p < 0.01) and for fair quality embryos than poor (61% vs. 48%, p < 0.01). There was no significant difference in the euploidy rate between good and fair quality embryos (64% vs. 61%, p = 0.56). Embryos biopsied on day 5 were more likely to be euploid than embryos biopsied on day 6 (59% vs. 50%, p < 0.01) or day 7 (59% vs. 37%, p < 0.01). There was no significant difference in the euploidy rate between day 6 and day 7 embryos (50% vs. 37%, p = 0.07). Conclusion: PGT-A may be more useful in cycles where a lower euploidy rate is expected based on age at oocyte retrieval, embryo morphology, and day of biopsy. There may be little benefit to biopsy of embryos with a high euploidy rate. Young patients with one or more good quality day 5 embryos may benefit from a “transfer the best fresh and biopsy the rest” strategy.