Successful Pregnancy and Delivery After Detection of a Super Early Window of Implantation with Endometrial Receptivity Analysis (ERA), A Case report.

Abstract Background: This is the first reported case of the world's shortest implantation window, where a blastocyst was transferred onto the endometrium during an extremely early implantation window identified by ERA, resulting in a successful pregnancy and birth. Case presentation: A 35-year-old nulligravida, nullipara presented with a history of 10 failed timed intercourse cycles and 4 unsuccessful intrauterine inseminations (IUIs). The patient exhibited ovulatory dysfunction, irregular menstruation, and polycystic ovarian syndrome. Despite initial ovarian stimulation and the retrieval of good-quality blastocysts, repeated embryo transfer attempts were either canceled due to inadequate endometrial thickness or resulted in implantation failure. Consequently, an Endometrial Receptivity Analysis (ERA) was performed. Persistent ERA tests following repeated post-receptive results ultimately led to the detection of an unusually early window of implantation, occurring just 67 hours after progesterone exposure. ERA-guided embryo transfers enabled implantation, but repeated attempts resulted in miscarriage, chemical pregnancy, or failure to implant. After additional oocyte retrieval and 11 embryo transfer attempts, the patient ultimately achieved a successful pregnancy and delivered a healthy baby at term. Conclusions: To our knowledge, this case presents the earliest documented window of implantation with a subsequent live birth. It underscores the existence of scenarios where the timing of implantation may occur at unexpected intervals, significantly deviating from expectations based on prior knowledge and clinical experience. This case further highlights the importance and practical value of ERA in managing such cases.