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Updated: Feb 8, 2026
Protocol for Human Blastoids Modeling Blastocyst Development and Implantation
Published on: August 10, 2022
Blastocyst development rate influences implantation and live birth rates of similarly graded euploid blastocysts
Mohamad Irani1, Claire O'Neill1, Gianpiero D Palermo1
1Ronald O. Perelman and Claudia Cohen Center for Reproductive Medicine, Weill Cornell Medicine, New York, New York 10021.
Objective:
To determine whether the blastocyst development rate, as assessed by the day of trophectoderm biopsy (day 5 vs. day 6), affects the live birth rate (LBR) of similarly graded euploid blastocysts.
Design:
Retrospective cohort study.
Setting:
Academic medical center.
Patient(S):
Patients who underwent frozen-thawed single euploid blastocyst transfers from 2013 to 2016 were included. Blastocyst morphologic grading was performed on day 5 or day 6 before the biopsy, with embryos designated into the following groups: good (3-6AA, 3-6AB, and 3-6BA), average (2-6BB), and poor (2-6BC and 2-6CB).
Intervention(S):
Frozen-thawed embryo transfer.
Main Outcome Measure(S):
Implantation rate (IR) and LBR.
Result(S):
A total of 701 frozen-thawed single euploid blastocyst transfer cycles were included. Cycles in which day 5 blastocysts were transferred (n = 366) were associated with a significantly higher LBR than those in which day 6 blastocysts were transferred (n = 335; 60.4% vs. 44.8%). The odds ratio remained significant after controlling for all confounders, including the blastocyst grading. Furthermore, there was a significant difference in LBRs between good-quality, average-quality, and poor-quality blastocysts (67.8%, 53.4%, and 29.5%, respectively). Embryos reaching good-quality blastocysts on day 5 yielded significantly higher LBR (72.8% vs. 56.5%) and IR (77.7% vs. 58.7%) compared with those reaching similar quality blastocysts on day 6. Similarly, day 5 average-quality embryos conveyed a significantly higher IR compared with day 6 embryos of the same quality (64.4% vs. 53.4%).
Conclusion(S):
In addition to aneuploidy assessment, the speed of embryo development to the blastocyst stage and an evaluation of blastocyst morphology are critical to selecting the best embryo.
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