Recurrent implantation failure: a comprehensive review.

Successful pregnancy involves a synchronized, coordinated cross-talk between an embryo capable of implanting, and an endometrium enabling implantation. Recurrent implantation failure (RIF) refers to unsuccessful implantation after repeated transfers of morphologically good quality embryos into a normal uterus. The etiology for RIF can be attributed to the embryo itself, the mother or, in some cases, both. Despite extensive research on underlying causes for RIF, our understanding of this condition is still limited. With the evolving molecular technologies, efforts are focused on studying the implantation process itself, including the molecular aspects of endometrial-embryonic interactions, normal human embryonic development, and preimplantation genetic evaluation. This knowledge will pave the way toward new diagnostic and therapeutic strategies for RIF. In this article, we present a comprehensive review of our current knowledge on this topic.