Immature oocyte proportion may or may not compromise ICSI outcomes, but methods do: a critical appraisal

Dear Editors, We read with interest the article entitled ‘A high proportion of immature oocytes in a cycle cohort does not compromise embryo development or live birth rates after ICSI’ (Sripada et al., 2025). The data set is large, and the clinical question is important. However, we feel that several choices in the methodology and the way the results are presented do not fully support this message. First, it is important to distinguish between the proportion of mature oocytes and the absolute number of mature oocytes obtained in a cycle. When cycles are matched on MII count, the analysis no longer addresses whether a low MII proportion reduces cycle-level or patient-level live birth chance. It only compares a selected subgroup of cycles in which the same number of MII oocytes was obtained, and an embryo transfer was performed. In such a restricted subgroup, it is not surprising that live birth per transfer can look similar. We believe it is important to state clearly that the main analysis addresses live birth per transfer in a selected subgroup, not live birth per oocyte retrieval or per patient.