To investigate whether ovarian response to controlled ovarian stimulation (COS) for medical fertility preservation differs according to the underlying indication, comparing oncological and benign conditions.

This retrospective cohort study included women undergoing fertility preservation by oocyte vitrification for oncological or benign medical indications between 2019 and 2023. Ovarian response to COS was evaluated using the number of retrieved mature metaphase II oocytes, the ovarian sensitivity index (OSI), and the follicular output rate (FORT). To account for differences in baseline ovarian reserve, a propensity score matching (PSM) analysis was performed based on age, anti-Müllerian hormone (AMH), antral follicle count (AFC), and body weight.

A total of 315 patients were analyzed (136 oncological and 179 benign indications). Cycle cancellation due to poor ovarian response occurred more frequently in the benign group (22.3%vs 3.68%). In unadjusted analyses, oncological indications were associated with a higher number of retrieved mature oocytes and higher OSI values. After PSM, OSI was no longer significantly different between groups, whereas the number of mature oocytes retrieved remained slightly higher in the oncological group. FORT suggested differences in follicular development patterns between indications but was available in a limited subset of patients and should be interpreted cautiously.

Differences in ovarian response to COS between oncological and benign fertility preservation indications appeared to be largely related to differences in baseline ovarian reserve. Although ovarian sensitivity appeared broadly similar after adjustment, the benign group had a substantially higher cancellation rate and a slightly lower mature oocyte yield. FORT, assessed in a limited subset, remains exploratory and should not be overinterpreted.