Physiology and pathology of implantation in the human and nonhuman primate

Infertility affects 10 to 15% of the general population, and although advances in assisted reproductive therapies have had a major input, pregnancy rates continue to be relatively low. This has lead to an increasing interest in understanding the interaction between the embryo and the endometrium during the window of implantation. Multiple experimental approaches have been used to evaluate the morphological, cellular, and molecular changes in the endometrium during the normal menstrual cycle and as a consequence of numerous benign gynecological diseases that contribute to infertility. Successful implantation requires interplay between the embryo and the endometrium during a very narrow window of time within the menstrual cycle. Given that there are limitations to evaluating this intricate dialog in the human, nonhuman primates serve as a valuable model by which to obtain insights into this critical period of uterine receptivity. Articles in this issue provide a comprehensive summary of approaches to understand the complex biology that is required for successful implantation, and the potential adverse consequences of ovarian hyperstimulation and benign gynecological diseases on uterine receptivity and embryo implantation.