Extended 35 to 38 hours after HCG priming for immature oocyte retrieval increases oocyte maturation rate in IVM treatment

Abstract

To evaluate whether extending the interval from HCG priming to immature oocyte retrieval increase oocytes maturation rate following in vitro maturation (IVM). Retrospective analysis comparing of oocyte maturation rate in immature oocytes retrieved 35 h (group 1) and 38 h (group 2) after HCG priming. 100 patients with polycystic ovary syndrome (PCOS) for IVM treatment were included in this study. Oocyte retrieval was performed between day 9 to day 16 of the menstrual cycle based on the patient's cycle length. When the endometrium thickness reached to ≥6 mm, 10,000 IU human chorionic gonadotropin (HCG) was given. Between January 1, 2006 to February 9, 2006, immature oocyte collection was performed after 35h HCG priming (group 1; n = 87) and between February 13, 2007 to April 21, 2007, immature oocyte retrieval was performed 38 h after HCG priming (group 2; n = 17). Following oocyte retrieval, the maturity of oocytes was assessed and the mature oocytes were subjected insemination by intracytoplasmic sperm injection (ICSI) 3 hours after collection. The remaining immature oocytes were cultured in IVM-medium (Coopersurgical/SAGE) supplemented with 75 mIU/mL FSH and LH up to 48 h. Fertilized zygotes were cultured in Embryo Maintenance Medium (Coopersurgical/SAGE), and the resulted embryos were transferred. There was no difference in the mean number of oocytes retrieved (16.3 ± 9.2 vs. 15.2 ± 9.1) between two groups. However, on the day of oocyte retrieval, the rate of matured oocytes collected was significantly higher (P< 0.01). in group 2 (15.1%, 39/258) compared to group 1 (8.3%, 118/1416). In addition, oocyte maturation rate after 24 h IVM was significantly higher (P< 0.01) in group 2 (54.3%, 119/219) compared to group 1 (36.4% 338/1298). The total maturation rate after 48h IVM was significantly higher (P< 0.05) in group 2 (72.1%, 186/258) compared to group 1 (65.5%, 928/1416). Although fertilization and the cleavage rates were comparable between two groups, the clinical pregnancy rate seems higher in group 2 compared to group 1. The results suggest that extending the HCG priming time from 35 hours to38 hours for immature oocyte retrieval promotes more oocyte maturation in vivo and obtains higher in vitro maturation rate of immature oocytes. Therefore, immature oocyte retrieval following 38 hours of HCG priming may improve subsequent pregnancy outcome of IVM treatment.