Assessing receptivity in the endometrium: the need for a rapid, non-invasive test

Successful implantation of an embryo into the uterus requires synchrony between the blastocyst and the endometrium. Endometrial preparedness, or receptivity, occurs only for a very short time during the mid-secretory phase of the menstrual cycle in fertile women. Failure to achieve receptivity results in infertility and is a rate-limiting step for IVF success. Frozen embryo transfer in non-stimulation cycles is already improving live birth rates. However, an important tool that is missing in the armoury of reproductive specialists is a means to rapidly assess endometrial receptivity, either during initial assessment or immediately prior to embryo transfer. The development of a wealth of omics technologies now opens the way for identifying potential receptivity markers, although validation of these is still a major issue. This review assesses the current state of the field and the requirements to proceed to a valid clinical test.