[Endometrial preparation in oocyte recipients].

Oocyte donation is offered to patients with premature ovarian failure to achieve pregnancy when no other assisted reproductive technology is possible. Some clinical and biological factors have been identified for influencing the outcome of oocyte donation cycles. Embryo implantation depends on embryo quality, method for the embryo transfer, and endometrial differentiation. In our center, the oocyte recipients receive for the endometrial preparatory cycle the same treatment that for the patients undergoing frozen embryos transfers, with good clinical pregnancy rates, about 35% per transfer. Estrogen and progesterone supplementation with GnRH agonist down regulation are used in synchronized protocols or for frozen embryos transfers. The synchronization between recipient's endometrium and donor's ovarian stimulation is very restrictive. Nowadays, the oocytes vitrification lithens the oocyte donation process: the endometrial preparation has a limited duration and is well controlled, and embryos that are transferred are all fresh embryos.