Fertilized egg into the uterus about 6-7 days, sperm through the cervical enclosure into the uterine cavity as well as the fallopian tube cavity, inside the fallopian tube and the egg to meet and combine into a fertilized egg, fertilized egg with the peristalsis of the fallopian tube as well as fallopian tube epithelial cilia to promote the direction of uterine cavity run, in the process of fertilized egg will undergo mitotic division, the formation of a number of sub-cells. The fertilized egg reaches the uterine cavity when it divides into an early blastocyst, and implants into the endometrium through three stages of localization, adsorption, and penetration, thus completing the process of implantation, at which time the trophoblast cells begin to secrete chorionic gonadotropin, which maintains the life span and function of the corpus luteum.