Abstract: The preimplantation embryonic developmental capacity determined the pregnancy outcome.Morphological assessment asa non-invasive technology was the most commonly method in ART to evaluate thepreimplantation embryo vitality. It will provide the prediction of embryonic development and clinical pregnancyto establish the grading standard of oocyte and embryo morphology. There are special characteristics for eachdevelopmental stage of embryos. In general, it is difficult to identify which embryo has the developmentalvitality of the implantation stage embryo at a time point. It is necessary to set up a continuous embryo scoringsystem including the pronuclear score, early cleavage and cleavage stage embryo scores in order to select theproper embryo for transfer morphological parameters could not accurately reflect the potential of embryodevelopment because the accuracy of morphological assessment was still not good enough. Embryo researchershave been devoted to exploring the objective evaluation of embryonic development potential in order to guideclinical protocol adjustments. High-quality embryos were selected for transplantation effectively improved theclinical outcome of assisted reproductive technology and reduced multiple pregnancy.

Key words: Embryonic development, Embryo transfer, Reproductive techniques, assisted, Pregn