Embryo implantation during menstruation in the absence of adequate estradiol and progesterone support, with subsequent normal response to ovulation induction and superfetation

Objective: To report an unusual case of embryo implantation and superfetation. Design: Retrospective case analysis. Setting: Oak Brook Fertility Center. Patient(s): A 41-year-old woman underwent two consecutive ovarian stimulation cycles interrupted by a normal menstrual period. Ovulation and implantation occurred during both cycles. The first embryo conceived developed normally until term; the second failed to develop. Intervention(s): None. Main Outcome Measure(s): Retrospective analysis of stored blood samples for serum E-2, P, and beta-hCG levels. Result(s): Rising beta-hCG levels during menstruation indicated normal embryonic implantation in the absence of adequate E-2 and P support, During subsequent ovarian stimulation, there was a normal follicular and E-2 response and normal ovulation in spite of the ongoing pregnancy. The second embryo, conceived during the second cycle of stimulation, implanted but failed to develop. Conclusion(s): This unusual case indicates that E-2, P, and endometrial thickness requirements for successful implantation may not always be as critical as postulated previously. The absence of a decidual response might have facilitated superfetation. (C) 1997 by American Society for Reproductive Medicine.