Abstract: It is essential to block the adverse effects of premature LH surge on developmental oocyte in the process of the controlled ovulation stimulation. The traditional protocols of ovulation induction, such as gonadotropin-releasing hormone agonist and antagonist, have some disadvantages of increasing incidence of ovarian hyperstimulation syndrome, high cost and inconvenience. In 2015, Professor Kuang YP proposed the progestin primed ovarian stimulation protocol (PPOS), in which exogenous progesterone was used to inhibit LH peak, and to combine with human menopausal urinary gonadotropin (hMG) to stimulate ovulation. PPOS protocol had been proved to be effective in inhibiting premature LH peak, obtaining good quality embryos and satisfactory clinical outcomes in women with all kinds of ovarian reactions. At present, progesterone drugs used in PPOS protocol include medroxyproges acetate, utrogestan and dydrogesterone. It is also necessary to concern the security of PPOS protocol. We reviewed the mechanism of PPOS protocol, the application population, the effeciency of different progesterone drugs, the effects on the quantity and quality of oocytes retrieved and the clinical outcomes, as well as the safety of newborn.

Key words: Follicular phase, Ovulation induction, Oocytes, Embryonic development, Progesterone