Role of Endometrial Receptivity in Unexplained Infertility

Unexplained infertility is a diagnosis of exclusion after the standard tests for ovulation, tubal patency, and sperm have been performed. Some of the patients with unexplained infertility may have abnormal endometrial receptivity. Human implantation is a group of processes which is complex and is far from being completely understood. During the time of implantation not only structural but molecular changes also occur. The “window of implantation” (WOI) is defined as the phase in which the endometrium is receptive to the embryo. The first attempt to evaluate the endometrium was with conventional histology and specific changes were noted based on days of progesterone exposure. However, this is not an accurate or reliable evaluation of the endometrium. Ultrasound evaluation of the endometrium can provide limited value in the study of endometrial receptivity regarding uterine contractility and perfusion. Multiple advances to identify molecular markers have been achieved although it is unlikely that a single molecule can be used in the clinical setting due to the inherent complexity and overlap of molecules and receptors related to implantation. A test of endometrial receptivity using genomic technology appears promising as a customized microarray with selected genes that have been described to be important during the WOI is able to identify endometrial samples that are thought to be “receptive” regardless of their histology.