Embryo implantation is absolutely dependent on the preparation of the uterus to the
receptive stage and attainment by the blastocyst of implantation competency. Co-ordinated
effects of progesterone and oestrogen are essential for these processes and determine the
window of implantation. In rodents, a generalized stromal edema occurs before blastocyst
attachment followed by uterine luminal closure. This leads to apposition of the blastocyst
trophectoderm against the luminal epithelium and ultimately attachment. Progesterone is …