What is the optimal age for elective oocyte freezing?

[Protocol elements verified against ESHRE Ovarian Stimulation Guideline 2026; age counselling is Tier B] On protocol, ESHRE (2026) is specific: Stimulation for elective oocyte preservation can be started irrespective of the menstrual cycle phase (conditional). GnRH antagonist or progestin protocols are probably recommended over GnRH agonist protocols for pituitary suppression in elective oocyte cryopreservation (conditional). For final oocyte maturation in elective oocyte cryopreservation, a GnRH agonist is preferred (good practice point). On age, the honest position: the biology is unambiguous in direction but no guideline I have verified specifies an optimal age. Oocyte yield and euploidy both decline with age, so earlier freezing produces more usable oocytes per cycle. Against that, most women who freeze never return to use their oocytes, so freezing very early means many women undergo stimulation they will not need. What should therefore be counselled rather than a single number: Expected oocyte yield at her age and AMH/AFC, and how many cycles that implies. That the number of mature oocytes stored, not the age at freezing, is what determines the chance of a live birth. That freezing is not a guarantee, and that the age at which she would return to use them matters for the pregnancy itself. Cost across multiple cycles, and storage duration and cost. Reviewer: if you wish to state an age range, cite a specific source. This answer deliberately does not, because I could not verify one.