Progestin-primed ovarian stimulation (PPOS) is an IVF stimulation protocol in which a progestin medicine, rather than a GnRH agonist or antagonist, is used to prevent a premature LH surge during stimulation. Because progestins prevent ovulation while allowing follicle development, this approach is generally used only with a plan to freeze all embryos rather than perform a fresh embryo transfer in the same cycle, since the progestin affects the lining of the uterus. PPOS may be considered for women without an urgent need for a fresh transfer, for fertility preservation, or in specific clinical situations judged appropriate by the treating fertility specialist. It is one of several protocol options and is not suitable for every patient.
Also known as: PPOS
Sources
- ICMR Standard Treatment Workflows (icmr.gov.in/standard-treatment-workflows-stws)
Last reviewed: 9 September 2026. Written by the Antega Editorial Team. General information only — always follow the advice of your own clinic, doctor or pharmacist.