Endometrial receptivity in the midluteal phase of the menstrual cycle, known as the window of implantation (WOI), occurs only for a very short period of time. However, so far, there is no reliable clinical and biochemical indicators of WOI. Therefore, this study is to correlate and identify the biochemical markers which may reflect WOI.~participants will be asked to be:~performed endometrial biopsy~taken blood for a few time points (e.g. pre-conception and being pregnant) and to compare different kinds of biochemical markers.
The aim of this study is to correlate and identify the biochemical markers which may reflect WOI. Blood samples will be collected and endometrial biopsy will be performed at particular time points.