For the grade of IVF embryos, they are actually graded according to the quality of embryos, which are usually classified into four grades, i.e. A, B, C and D. It is one of the main factors affecting the success rate of IVF. The specific grading is as follows: 1. Grade A: i.e. excellent embryos, these embryos have normal refraction of the ovoid sphere, uniform size, regular appearance, complete and smooth zona pellucida, less than 10% or no amount of debris, the most desirable embryos in IVF, embryonic cell clusters are uniform and symmetrical spherical, individual ovoid spheres or cells are uniform in size, color and density, and the developmental stage of the embryo is consistent with the expected developmental stage; 2. Grade B Grade B: are good embryos, these are fertilized eggs with average refractive index of the ovoid sphere, less uniform size, less than 20% fragmentation, some irregularity in the size and shape of the cell mass and the color and density of individual cells, these are the most common embryos for IVF; 3, Grade C: are average embryos, embryos with severe irregularity in the size and shape of the cell mass and the color and density of individual cells. At least 25% of the cell structure is intact with an active embryonic cell mass. The use of these embryos will reduce the success rate of IVF and the doctor will usually inform the patient couple before the transfer and use them only if the patient insists on using them, or not use these embryos if the patient gives up. 4. Grade D: Unusable embryos, signifying the death or degeneration of the embryo.