Recent studies have presented apoptosis as the key mechanism of endometrial tissue reconstruction. Regulation of apoptosis leads to the menstruation or prepare the mucose layer for the implantation of the embryo. Thus, the factors controlling apoptosis determine proper endometrial preparation for blastocyst implantation. Among these factors, not only the progesterone but also embryonic factors (chorion gonadotropin) and those produced by endometrium affected by interaction with blastocyst (prolactin, IGFBP-1) plays the pivotal role.