Introduction: Endometrial function: facts, urban legends, and an eye to the future.

The embryo alone, though very important, is not sufficient to explain successful or failed implantation. Human embryonic implantation is less efficient than in nonmenstruating species. The main difference lies in the decidual control of early implantation events and the subsequent course of pregnancy versus embryo control in nonmenstruating species. In this article, we introduce the facts behind the low efficiency of this crucial process, address urban legends routinely considered without high clinical quality evidence, and provide a vision of how the endometrial field will develop in the near future.