Defective endometrial receptivity.

The endometrium is one of the most fascinating tissues in the human body. Its sole purpose is to enable implantation of an embryo during a relatively short window of opportunity in the menstrual cycle. It is becoming clear that overcoming the current bottleneck in improvements to assisted reproductive techniques will require a closer look at the interface between uterus and embryo. Indeed, embryo implantation requires a cross talk with a receptive endometrium. Using sonography, hysteroscopy and endometrial biopsy we can learn about anatomical and functional markers of endometrial receptivity. This article reviews the factors which might cause defective endometrial receptivity. These include uterine polyps, septa, leiomyomata and adhesions. The effect of thin endometrium, endometriosis and hydrosalpinx is also described. Finally contemporary investigation of molecular markers of endometrial receptivity is described. Improving embryo implantation by a closer look inside the uterus is the key to increasing pregnancy rates in IVF.