Whether it is suitable to transfer 5-day blastocysts after 21 eggs are retrieved depends on the good or bad quality of embryos at the cleavage stage and personal situation, and it is recommended to follow the doctor’s advice to choose. Blastocyst is the final stage of in vitro culture of embryo, usually formed on the 5th day after fertilization of egg. Blastocyst transfer in IVF treatment can get high embryo implantation rate, if the quality of embryo at cleavage stage is better, you can transfer 5th day blastocyst under doctor’s advice. The appropriate people for blastocyst transfer are as follows, patients with chromosomal abnormality who need to wait for embryo biopsy results, patients with multiple IVF failures, patients with more embryos, and those whose endometrium is not synchronized with the development of embryos. Blastocyst transfer requires higher in vitro culture conditions, which makes it technically difficult, and the embryos may stop developing or degenerate, and whether to choose blastocyst transfer should be different from one person to another. It is recommended to go to a regular hospital for IVF transfer to improve the success rate of the transfer.