Programing the onset of ovarian stimulation: From early follicular phase start to oral contraceptive (OC) pill, to luteal phase E2, Duo-Stim and random start OS protocols.

Ovarian stimulation has been the single most efficient measure ever taken in ART for improving outcome by harvesting multiple oocytes and ultimately, embryos. Today, ovarian stimulation protocols consist in administrating exogenous gonadotropins in order to override the natural mechanisms which controls the ovulatory quota to one in humans. For practicality issues, there has been numerous attempts to control, or 'program', when ovarian stimulation are initiated in order to improve functionality and in turn efficacy for ART programs. The different options for controlling the onset of ovarian stimulation currently available are discussed here, as well as the novel possibility of using progestins for blocking premature ovulation.