Vitrification of Human Germinal Vesicle Oocytes: before or after In Vitro Maturation?

The use of immature oocytes derived from stimulated cycles could be of great importance, particularly for urgent fertility preservation cases. The current study aimed to determine whether maturation (IVM) was more successful before or after vitrification of these oocytes. This prospective study was performed in a private fertilization (IVF) center. We collected 318 germinal vesicle (GV) oocytes from 104 stimulated oocyte donation cycles. Oocytes were divided into two groups according to whether vitrification was applied at the GV stage (group 1) or matured to the metaphase II (MII) stage and then vitrified (group 2). In the control group (group 3), oocytes were matured without vitrification. In all three groups, we assessed survival rate after warming, maturation rate, and MII-spindle/chromosome configurations. The chi-square test was used to compare rates between the three groups. Statistical significance was defined at P