Blastomere cleavage plane orientation and the tetrahedral formation are associated with increased probability of a good-quality blastocyst for cryopreservation or transfer: a time-lapse study

Objective: To determine whether blastomere spatial arrangement in early human embryos is reflective of embryonic potential. Design: Retrospective analysis of prospectively collected data. Setting: Single academic center. Patient(s): Patients undergoing a single blastocyst transfer. Intervention(s): None. Main Outcome Measure(s): Developmental kinetics, blastocyst quality, embryo dysmorphisms, and live birth rate. Result(s): A total of 716 embryos were examined in detail for cleavage plane orientation, blastomere arrangement, and morphokinetic behavior. Tetrahedral (TET) and nontetrahedral embryos (nTET) differed significantly in developmental kinetics. The frequency of dysmorphisms, multinucleation, and irregular chaotic division was higher in nTET embryos. Only 44% of nTET versus 62.9% of TET embryos were scored as top-quality blastocysts. After adjusting for age, our data indicated that having TET embryos significantly increased the odds of having a blastocyst for cryopreservation/transfer (odds ratio, 3.58; confidence interval, 2.42-5.28) when compared with nTET. A total of 164 fresh single ETs were performed with blastocyst-stage embryos. The implantation rate for TET- and nTET-derived blastocysts were similar (64.7% and 62%, respectively). The live birth rate was 55% in both groups. A meridonal first division was noted in 85% of the fresh SET blastocysts. Conclusion(s): Cleavage plane orientation during the first three divisions appeared to dictate final blastomere spatial arrangement. The TET formation at the four-cell stage was predictive for embryos most likely to develop into good-quality blastocysts for cryopreservation/transfer. Morphokinetic markers of embryo potential were significantly different between TET and nTET embryos. (Copyright (C) 2019 The Authors. Published by Elsevier Inc. on behalf of the American Society for Reproductive Medicine.)