Implantation defect in endometriosis: endometrium or peritoneal fluid

Clinical observations indicate that an implantation defect occurs in women with endometriosis. Despite intense research, the role of alterations in en dometrial receptivity and the peritoneal fluid microenvironment in the dera ngement of implantation in endometriosis remains controversial, in this rev iew, the evidence for the altered endometrial receptivity and peritoneal en vironment are summarized, and their effects on the implantation defect in w omen with endometriosis are discussed. Recent studies on cell adhesion mole cules and their ligands, apoptosis, homeobox genes and the direct action of gonadotrophin-releasing hormone analogues are reviewed with respect to the ir contribution to endometrial receptivity in endometriosis. The possible m echanisms by which an altered peritoneal environment of endometriosis may a ffect implantation, including cytokine concentrations, iron metabolism, bio chemical factors and embryotoxicity are discussed.