*2.10. Endometrial Receptivity Array*

Recently, a customized endometrial receptivity array (ERA), containing 238 genes related to endometrial receptivity, was created [200]. These genes, differentially expressed in the receptive phase, encode for factors involved in several biological processes, such as processes related to the immune system, circulation, response to external stimulus, behavior, cell cycle, cell adhesion, anatomical structure development, cell–cell signaling, and mitotic cell cycle [200]. Beside the many above mentioned genes suggested to regulate endometrial receptivity, additional genes have been identified by ERA, highlighting the great complexity of factors regulating implantation. ERA has been suggested as a more accurate and reproducible approach to assess endometrial receptivity compared to histological analysis [201] and its use has been proposed for RIF patients [202]. Considering how critical the molecular signature of the endometrium is for embryo implantation, a test which unequivocally assess if the embryo and the uterus are in synchrony may be of great value to avoid ineffective embryo transfers. However, the utility of ERA in the clinical practice is still debated [203]. More recently, a smaller set of genes has been proposed to assess the receptivity status of the endometrium in biopsies obtained in the secretory phase [204]. It is reasonable to foresee new additional advances in this area, that is of potential great clinical utility in the management of infertile women undergoing IVF, as well as in women with RIF and unexplained RPL.
