In vitro maturation rate of immature oocytes according to presence of in vivo matured oocytes

Abstract

OBJECTIVE: The purpose of this study was to investigate the in vitro maturation rate of immature oocytes according to presence of in vivo mature oocytes in unstimulated in vitro maturation (IVM) cycles. DESIGN: Retrospective study. MATERIALS AND METHODS: 282 patient who underwent unstimulated IVM cycles were included. Without ovarian stimulation using exogenous gonadotrophins, transvaginal ultrasound was performed every 2-3 days from menstrual day 3 to check endometrial thickness and ovarian follicles. Ovulationwas inducedwith urinary or recombinant hCGwhen endometrium reached more than 6mm in thickness, and transvaginal oocyte retrieval was performed 36 hours later. Cumulus cells were removed after oocyte retrieval for assessment of maturity. Among the retrieved oocytes, mature ones were fertilized within 5 hours. The immature ones were subsquently matured in vitro in culture medium for 24-48 hours. After confirmation of maturation, the oocytes were fertilized using intracytoplasmic sperm injection technique. RESULTS: Mean age of the study subjects was 32.4 3.0 years and mean body mass index was 22.7 13.1 Kg/m. Mean blood level of AMH was 10.0 5.2 ng/mL and mean number of total retrieved oocytes was 17.1 8.4. A significant negative correlation was noted between % mature oocytes on retrieval and in vitro maturation rate of immature oocytes (p1⁄40.001, R1⁄4-0.191). In cycles in which mature oocytes were retrieved (n1⁄4125) and not (n1⁄4157), the in vitro maturation rate of immature oocytes were 60.8 19.0% and 66.6 14.7% (P1⁄40.004) respectively. But there were no significant differences in total %mature oocytes (67.0 15.1% vs 66.0 14.3%, p1⁄40.60), fertilization rate (53.3 17.0% vs 52.5 14.1%, p1⁄40.66) and pregnancy rate (37.6% vs 35.0%, p1⁄40.66) between two groups. CONCLUSION: In unstimulated IVM cycles, in vitro maturation rate of immature oocytes was lower when naturally mature oocytes were retrieved. But the presence of in vivo mature oocytes doesn’t affect total oocyte maturation rate, fertilization rate and pregnancy rate.