Endometrial receptivity (ER) refers to the receptivity of the mother's endometrium to the blastocyst, which is an important factor affecting the success of embryo implantation in addition to the quality of embryo. Endometrial receptivity assessment (ERA) can predict when the uterus is most likely to receive embryo implantation, that is, WOI. Therefore,test of endometrial receptivity and embryo transfer in implantation window can greatly improve the clinical pregnancy rate of IVF-ET.

Endometrial receptivity assessment (ERA) is to evaluate endometrial receptivity through different indicators and techniques. When the endometrium is in the receptive phase, it is generally considered to be WOI. The standard WOI is usually 19-21 days of the menstrual cycle.

Reference

[1] The role of the endometrial receptivity array (ERA) in patients who have failed euploid embryo transfers.J Assist Reprod Genet. 2018 Apr;35(4):683-692