Unusual case of embryo implantation & superfetation

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.

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 E2, P, and β-hCG levels.

Result(s): Rising β-hCG levels during menstruation indicated normal embryonic implantation in the absence of adequate E2 and P support. During subsequent ovarian stimulation, there was a normal follicular and E2 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 E2, 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.

Source: Fertility and Sterility, Volume 68, Issue 3 , September 1997, Pages 538-541