Along with the advancement of embryo culture solution and culture technology, blastocyst culture has become a further screening method, i.e., day 3 embryos will continue to be cultured in vitro for 2-3 days, and the morphology of the embryos will be observed again in order to determine whether there is any potential for further development, and during this process, the embryos with poor quality and developmental potential will be eliminated from the embryos and their development will be stagnated, so as to filter out the higher quality embryos. Of course, the quality of day 5 blastocysts is also evaluated from the point of view of their appearance, and there is also the disadvantage of “judging a book by its cover”, but compared to day 3 embryos, the appearance of day 5 embryos is one step closer to the true developmental ability of the embryo. In addition, under normal physiological conditions, the day 3 embryo exists in the fallopian tube, the day 3 culture in the uterus after transplantation and can not be hatched in time to adhere to the surface of the uterine lining, will travel in the uterine cavity or travel to the fallopian tube, if both fallopian tubes proximal obstruction, the uterine environment is not suitable for cleavage of the embryo development, it will result in a low rate of pregnancy; if the tubes through or distal obstruction, the embryo can not be in a certain period of time in the fallopian tube travel to the uterine cavity, the embryo can not be in a certain period of time to travel to the uterine cavity. certain time to travel to the uterine cavity, then it leads to the occurrence of ectopic pregnancy, which is why IVF-assisted pregnancy patients also have the possibility of ectopic pregnancy. The vitrification method of freezing embryos is superior to the traditional slow freezing, while blastocysts are more suitable for vitrification, i.e., blastocysts are frozen with less damage. Blastocyst transfer is a technique that offers real benefits to patients in terms of increased success rates, reduced costs associated with repeated failures, and the expectation of a healthy, normal child.