The window of implantation is the period of time when the endometrium is ready to receive the embryo. This time interval usually corresponds to days 19-21 of the menstrual cycle if the woman has regular cycles.
However, the window of implantation may be temporarily displaced. This would imply embryo implantation failure, even if the embryos are of good quality, since they would not be transferred at the right time when the endometrium is receptive.
Currently, there are endometrial receptivity tests that indicate whether the endometrium is receptive or not and, if not, when is the right time to perform the embryo transfer. In this way, a personalized transfer is performed, which would increase the chances of success of the assisted reproduction treatment.
The endometrium undergoes changes throughout the woman's menstrual cycle, under the influence of ovarian hormones. The menstrual cycle begins with the onset of menstruation when the endometrium is shed and eliminated, as it will regenerate during the menstrual cycle that is beginning.