Low grade embryos will affect the transfer success rate and the success rate will be reduced. There are four grades of embryos for IVF, which are grade A embryo, grade B embryo, grade C embryo, grade D embryo, grade A embryo belongs to high-quality embryo, which is the ideal embryo for IVF, grade B embryo belongs to good embryo, which is the common embryo for IVF, grade C embryo has a smaller success rate, and grade D embryo is the unusable embryo without vitality. The success rate of IVF transfer will be relatively higher when the embryo grade is higher, but it is not absolute. Abnormalities such as biochemical pregnancy, fetal arrest and miscarriage may occur even if the embryo grade is higher, and the success rate of clinical transfer not only depends on the embryo grade, but also depends on the result of the embryo’s PGS (Preimplantation Genetic Screening). Embryo grade is a transfer standard for doctors to consider, helping them to determine which can be cultured to blastocysts and which can be frozen and resuscitated for processing, to maximize the success rate of IVF transfer.