Abstract: The blastocyst quality is very important for the elective single blastocyst transfer (eSBT). The multiple pregnancy rate can be effectively reduced, and the clinical pregnancy rate can be kept at a higher level, by transplanting a high-quality blastocyst. At present, the main method to evaluate the quality of blastocysts is morphology. The morphological parameters were comprehensively scored by the traditional morphological scoring method, which means that the blastocyst with higher score is of the better quality. However, when there are more than two blastocysts with the same score, new indicators are necessary for embryologists to select the blastocyst with the most developmental potential for transplantation. Three independent morphological parameters of blastocyst, inner cell mass (ICM), trophectoderm (TE) and degree of blastocyst expansion with the different predictive value for the pregnancy outcomes, can provide additional references for the further screening of the blastocyst. In recent years, the whole process of embryonic development can be observed dynamically by time-lapse imaging technology. The kinetic parameters of pronuclear stage, cleavage stage and blastocyst stage were tried as the new index for evaluating the quality of embryo. In this article, we reviewed the research progress on the screening high quality blastocyst by morphological and kinetic parameters.

Key words: Fertilization in vitro, Embryo transfer, Blastula, Morphogenesis, Kinetics