Progestin-primed ovarian stimulation

The use of progestins for the prevention of premature ovulation during ovarian stimulation is called progestin-primed ovarian stimulation (PPOS). Response to ovarian stimulation with PPOS and gonadotropin-releasing hormone (GnRH) analogs seem to be similar with the clinically insignificant differences being explained by endocrine characteristics as expected. PPOS has the advantage of oral administration and lower medication cost than GnRH analogs, but the mandatory cancellation of an otherwise possible fresh embryo transfer can render PPOS less cost-effective if a fresh transfer would have been possible. Oocytes collected in PPOS cycles have similar developmental potential, including blastocyst euploidy rates. Frozen embryo transfer outcomes of PPOS and GnRH analog cycles seem similar both in terms of ongoing pregnancy/live birth rates and obstetric and perinatal outcomes. While some studies reported lower cumulative live birth rates with PPOS, they suffer from methodological issues, including arbitrary definitions of cumulative live birth rates. PPOS has been used in all patient types with consistent results and seems a patient-friendly and cost-effective choice when a fresh embryo transfer is not intended.