ICSI is appropriate to achieving the higher fertilization rate of in vitro matured human oocytes collected from hCG-primed IVM/F-ET cycles.

Abstract

Objective: It has been suggested that in vitro maturation (IVM) of immature oocytes is a potentially useful treatment for women with high risk of OHSS. Qualitative changes, including zona hardening, occur in the zona pellucida during oocyte maturation in vitro, so that the fertilization rate might be reduced as used conventional IVF (DeFelici and Siracusa, 1982). Recently, Chian et al (2000), achieved the high fertilization rate through conventional IVF, reported that ICSI was not essential for the fertilization of IVM oocytes. To demonstrate a fertilization technique useful for IVM oocytes derived from IVM/F-ETs cycles, the fertilization rate was compared conventional IVF with ICSI. Design: IVM sibling oocytes were inseminated with either conventional IVF or ICSI and the fertilization rate was then compared with between two groups. Materials/Methods: The partners of patients (n = 75) had normal semen which proved in previous IVF cycles. Immature oocytes were collected on day 10–14 of a menstrual cycle. The patients were primed with either none (n = 54, group 1) or 10,000 IU hCG (n = 21, group 2) 36 hours before oocyte collection. A transvaginal ultrasound machine with 19-gauge aspiration needle was used to aspirate follicles between 5 and 14 mm in diameter. Follicular aspirates except for cumulus cell mass and cumulus-oocyte complexes (COCs) were filtered through 70-mm (in hole size) mesh and then COCs were isolated under a stereomicroscope. The normal COCs were cultured in maturation medium, a YS medium supplemented either with 70% (hFF in group 1) or with 30% hFF, 1 IU/ml rFSH, and 10 IU/ml hCG in group 2. After culture for 24 hours, the cumulus cells of COCs were removed with hyaluronidase and/or by mechanical pipetting and the nuclear maturity of oocytes was assessed on the basis of the first polar body under the dissecting microscope. The oocytes which did not still mature were cultured further (until 48 or 72 hours) in the same medium. IVM sibling oocytes were randomly divided into conventional IVF and ICSI for fertilization. Fertilization was assessed 17-19 hours after IVF or ICSI. Results: After culture for 24 hours, the IVM oocyte rate in hCG-primed group (60.1%, 194/323) was significantly higher than that in hCG-unprimed group (45.1%, 338/749 (P < 0.05). In the hCG-unprimed group, the fertilization rate through ICSI (82.1%, 151/184) was significantly higher than that of conventional IVF (69.5%, 107/154) (P < 0.05). In the hCG-primed group, the fertilization rate through ICSI (89.8%, 88/98) was also significantly higher than that of the conventional group (63.5%, 61/96) (P < 0.05). However, there was no difference of the fertilization rates between the hCG-unprimed group and the hCG-primed group. The fertilization rates of IVM oocytes from 25- to 72 hours were not investigated in this study because of oocyte-aging variation. Conclusions: This study suggests that ICSI is the best method for increasing the fertilization rate of IVM human oocytes derived from women undergoing IVM/F-ET cycles, although the acceptable fertilization could be achieved using conventional IVF. Supported By: Maria Hospital.