Embryo implantation window testing is often performed using endometrial tolerance analysis, which is a genetically-based endometrial tolerance test that requires the patient to undergo a simulated cycle of embryo transfer, where endometrial samples are collected at specific time points during the simulated cycle and sent to a laboratory for comparative analysis. For in vitro fertilization patients who are undergoing the embryo implantation window test, they are required to maintain the exact same medication regimen as in the simulated cycle. Based on the test report, the doctor will adjust the timing of the embryo transfer so that the embryos are implanted when the uterine lining is permissive to increase the conception rate. The embryo implantation window is a relatively short critical period of time when the endometrium allows the embryo to implant and is generally considered to be on day 22~24 of a normal menstrual cycle or on day 7 after the peak of luteinizing hormone. Moreover, the implantation window is a special period of time, the opening and closing of which is regulated by a variety of hormones, all of which may affect the success of the embryo transfer. Therefore, accurately mastering the period of embryo implantation window is the key to improve the success rate of IVF.