Initiation of ovarian stimulation independent of the menstrual cycle: a case-control study.

Purpose: In the GnRH-antagonist protocol, ovarian stimulation with gonadotropins typically commences on cycle day 2 or 3. Initiation of ovarian stimulation with a spontaneously occurring menstruation, however, poses significant organizational challenges for treatment centres and patients alike. It has previously been demonstrated in the context of fertility preservation that initiation of stimulation in the luteal phase is feasible in terms of retrieval of mature oocytes for cryopreservation.