The process of blastocyst implantation consists of three steps, namely positioning in the uterus, adhesion to the endometrium and invasion. For women who conceive naturally, the blastocyst usually develops into a blastocyst within a week or so after the union of sperm and egg, and then enters the uterus through the fallopian tube, after entering the uterus, the blastocyst will first be in a free state in the uterus, during which it will choose a location for implantation and wait for the conditions for implantation, such as the thickness of the endometrium needs to reach 8-10 mm, and the hormone levels in the body, such as progesterone, need to be maintained at normal levels. When the time is ripe, the blastocyst will adhere to the endometrium and then the trophoblast cells will differentiate and invade the endometrium to complete the whole process of blastocyst implantation. For IVF, the process of blastocyst implantation is similar to natural conception, except that the blastocyst enters the uterus by a different route.