Managing women with impaired response to ovarian stimulation has long presented challenges. Although the quantity of oocytes retrieved after stimulation is a criterion of POR used in clinical research, the threshold number for retrieval varies widely between studies. POSEIDON criteria intend to clarify the stratification of POR, integrating this aspect with age-related aneuploidy rates and ovarian sensitivity to gonadotrophins, thereby identifying the right therapy based on the individual woman’s clinical picture.