Blastocyst development rate influences implantation and live birth rates of similarly graded euploid blastocysts

The day of trophectoderm biopsy, reflecting the speed of embryo development to the blastocyst stage, and blastocyst morphology are critical parameters for selection among euploid embryos.

Volume 110, Issue 1, Pages 95–102.e1


Mohamad Irani, M.D., Claire O'Neill, B.S., Gianpiero D. Palermo, M.D., Ph.D., Kangpu Xu, Ph.D., Chenhui Zhang, M.D., Xiaoe Qin, M.S., Qiansheng Zhan, M.D., Ph.D., Robert N. Clarke, Ph.D., Zhen Ye, B.S., Nikica Zaninovic, Ph.D., Zev Rosenwaks, M.D.



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.


Retrospective cohort study.


Academic medical center.


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).


Frozen-thawed embryo transfer.

Main Outcome Measure(s)

Implantation rate (IR) and LBR.


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%).


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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