Fig. 2From: Competent blastocyst and receptivity endometrium improved clinical pregnancy in fresh embryo transfer cycles: a retrospective cohort studyDays of the menstrual cycle and the blastocyst WOI. Implantation is a complex process involving both the blastocyst and the maternal endometrium, and their interaction can only occur during a limited defined period, known as the WOI. Well-developed blastocysts adhere before or after the WOI and then miss the WOI. Note: E2: Estradiol, OVU: Ovulation, P4: Progesterone, WOI: window of implantationBack to article page