"Implantation Window" is defined as the stipulated time during which the endometrium is rendered receptive for incoming embryo. Outside of this time frame, it becomes non-receptive for implantation.
Despite several studies focussing on the most confounding factors affecting endometrial receptivity and embryo development, no substantial factors to increase the "take home" baby rate have been found. The intricate mechanism of implantation shall remain an enigma and increased live birth rates has been an achilles heel for embryologists and clinicians alike.
The implantation window is generally believed to encompass day 17 to day 24 of the menstrual cycle, during which embryonic development and endometrial preparation for implantation occur in tandem. It is seen that even the 'top quality' blastocyst transferred within the window period may fail to implant in an ultrasonographically detected healthy endometrium, if it is not in the right stage of development on that particular day of period when the transfer has been performed.
Blocked fallopian tubes is the most common cause of inability to conceive in such women. If the ovaries are affected, there is compromised ovarian function which is exhibited by markers of ovarian reserve - Anti-Mullerian Hormone (AMH) and AFC levels are much lower than normal.