The egg reaches the uterine cavity about 6-7 days after fertilization, and about 30 hours after fertilization, the fertilized egg moves toward the uterine cavity with peristalsis in the fallopian tubes and the pushing of the epithelial cilia in the fallopian tubes. The fertilized egg begins to undergo mitosis as it moves and then forms multiple daughter cells, reaching the uterine cavity in about 6-7 days. Some conditions are also needed for the fertilized egg to reach the uterine cavity and bed, 1. The gestational sac has to be synchronized with the development of the uterine lining and function in a coordinated manner, and the uterus has to have a sensitive period to allow the fertilized egg to bed. 2. The woman’s body needs to have enough progesterone so that the fertilized egg can be able to bed inside the uterine cavity. 3. The trophoblast cells inside the embryo have to be differentiated into ensheathed trophoblast cells, which are able to secrete chorionic Gonadotropins.