Should metaphase 1 and 2 stages oocytes be vitrified in the same time for fertility preservation?

Abstract

Aims: Could metaphase 1 (M1) and 2 (M2) stages oocytes from in vitro maturation (IVM) cycles and controlled-ovarian hyperstimulation (COH) cycles be frozen at the same time without any adverse effect of vitrification on further survival (SR) and maturation rates (MR)? Materials & methods: M1 from cancer patients were prospectively included in IVM/COH groups, and in study or control subgroups if they were vitrified or not. In each study subgroup, SR were compared with that of M2 oocytes vitrified/warmed from egg donors. MR were compared with those of fresh-M1 oocytes from control IVM/COH subgroups. Results: SR were not different between groups. MR compared respectively between survived- and fresh-M1 oocytes were similar when resulting from COH (85.2 vs 81.1%) but significantly lower after IVM (39.1 vs 73.3%). Conclusion: Simultaneous freezing of M1/M2 oocytes could be applied to COH but not to IVM during the course of fertility preservation.