ABSTRACT
INTRODUCTION e human endometrium is a complex tissue, predominantly composed of epithelial and stromal cells, that is cyclically and primarily regulated by steroid hormones (estrogens and progesterone). Endometrial receptivity is a self-limited period during which the endometrium transiently transforms to acquire the ability to receive a blastocyst and support implantation, a process that is mediated by immune cells, cytokines, growth factors, chemokines, adhesion molecules, and many other compounds (1-3). is transient period, called the window of implantation (WOI), has been postulated to open ve days aer endogenous or exogenous progesterone action and to close two days later (4,5). A receptive endometrium and a functionally normal blastocyst, as well as an exquisitely coordinated cross-communication between them, are required for implantation, the process by which the embryo attaches and invades the underlying maternal endometrial tissue.
