Synchronization of Donors and Recipients

Abstract

Synchronization of menstrual cycles between donors and recipients is essential to successful outcome in oocyte donation cycles. Although menstruation is the most obvious outward manifestation of ovarian cycle phase, synchronization of embryo and endometrial development is critical to optimize the outcome of oocyte donation. Synchronization of endometrial and embryo development must occur during all reproductive cycles, but in oocyte donation, the trajectory of embryo development is determined by factors distinct from those that influence endometrial development. This situation presents challenges to the clinician charged with orchestrating this transaction, but also provides opportunities to the clinical scientist committed to increasing our understanding of these earliest steps of human reproduction. Despite the urgency of the need to increase knowledge in this area, progress has been hindered by the limited applicability of animal models and the lack of valid in vitro models for human implantation, as well as by ethical constraints on experimentation involving human embryos. Nonetheless, progress in the biological basis of implantation, including endometrial changes and preimplantation embryo development, as well as in the clinical science of oocyte donation have enabled us to begin to develop a rational approach to synchronization of donor and recipient cycles.