Evaluation of the Endometrium in the XXI Century

The endometrium is a fundamental layer of the uterus that is relevant to female reproductive function. This specialized tissue lines the inner wall of the uterus and its condition and health are essential to the process of conception and subsequent embryo implantation. Since the early days of reproductive medicine, the maternal endometrium has been considered a passive part of the reproductive process; a "good quality embryo" was all that mattered. This fact requires revision since the efficacy of in vitro fertilization remains low despite considerable improvements in embryology and embryo transfer technologies in recent decades. We now know that human implantation is a very complex and multifactorial process. Successful implantation requires the presence of a healthy embryo, a receptive endometrium and a synchronized molecular dialogue between the two, as well as host immune tolerance/protection. The study of the endometrium is one of the fundamental aspects to be taken into account in assisted reproduction treatments. It is a necessary practice that is routinely performed in assisted reproduction clinics, specifically in cases of implantation failure and repeated miscarriage.