Ovarian follicular waves during the menstrual cycle: physiologic insights into novel approaches for ovarian stimulation.

Elucidation of multiple waves of antral ovarian follicular development during the menstrual cycle has challenged traditional concepts of female reproductive physiology and foundations of assisted reproductive therapies. Approximately two-thirds of women develop two follicle waves throughout an interovulatory interval and the remainder exhibit three waves of follicle development. Major and minor waves of follicle development have been observed. Major waves are those in which a dominant follicle develops; dominant follicles either regress or ovulate. In minor waves, physiologic selection of a dominant follicle is not manifest. Knowledge of waves of antral follicular development has led to the global adoption of novel ovarian stimulation strategies in which stimulation can be initiated at various times throughout the cycle. Random-start and luteal-phase ovarian stimulation regimens have had important clinical applications for women requiring urgent oocyte or embryo cryopreservation for fertility preservation prior to chemotherapy. Ovarian stimulation twice in the same cycle, referred to as double stimulation, may be used to optimize clinical outcomes in women with a poor ovarian response to stimulation as well as in those requiring fertility preservation before chemotherapy.