Oocyte maturity in repeated ovarian stimulation

OBJECTIVE: During stimulated IVF cycles, up to 15% of oocytes are recovered as immature. The purpose of this study was to investigate the trend of oocyte maturity in repeated ovarian stimulation for IVF. METHODS: One hundred forty-eight patients were selected who underwent two consecutive IVF cycles using same stimulation protocol during 2008 to 2010. Ovarian stimulation was performed with FSH and human menopausal gonadotropin and flexible GnRH antagonist protocol in both cycles. Oocyte maturity was assessed according to presence of germinal vesicle (GV) and the first polar body. Immature oocyte was defined as GV stage or metaphase I oocyte (GV breakdown with no visible polar body) and cultured up to 48 hours. If matured, they were fertilized with ICSI. RESULTS: Percentages of immature oocytes were 30.8% and 32.9% (p=0.466) and IVM rates of immature oocytes were 36.2% and 25.7% (p=0.077), respectively. A significant correlation was noted between percentage of immature oocytes in the two cycles (R=0.178, p=0.03). Women with >40% immaturity in both cycles (n=21) showed lower fertilization rate of in vivo matured oocytes (56.4% vs. 72.0%, p=0.005) and lower pregnancy rate (19.0% vs. 27.1%, p=0.454) after the second cycle when compared with women with <40% immaturity (n=70). In both groups, female age, number of total retrieved oocyte and embryos transferred were similar. CONCLUSION: In repeated ovarian stimulation cycles for IVF, the immature oocyte tended to be retrieved repetitively in consecutive IVF cycles.