IMMATURE OOCYTE RETRIEVAL - LESSONS FROM UNSTIMULATED IVF CYCLES

Objective: To describe retrieval of immature oocytes during unstimulat ed IVF and assess the in vitro maturation and fertilization rates. Des ign: Retrospective analysis. Setting: The USC program for assisted rep roduction. Patient(s): Spontaneously ovulatory women with predominantl y pelvic factor as their principal cause of infertility, under the age of 40, and no male factor.Intervention(s): HCG administration in mid- cycle, aspiration of all visible follicles, in vitro maturation of imm ature oocytes in culture media versus 50% follicular fluid in media, I VF, and embryo transfer. Main Outcome Measure(s): Rates of in vitro ma turation, fertilization, and implantation after embryo transfer. Resul t(s): A total of 101 immature oocytes were obtained during 59 follicle aspirations. Thirty percent of prophase I oocytes matured to metaphas e II in vitro compared with 44% Of metaphase I oocytes. Fertilization rates for matured prophase I oocytes were 62% for those cultured in st andard culture media (controls) and 87% for follicular fluid culture m edia. Two pregnancies resulted from the transfer of embryos derived fr om immature oocytes when no other embryos were transferred. Conclusion (s): Immature oocytes may be retrieved successfully during the mid-cyc le aspiration of the dominant follicle in unstimulated IVF cycles. Mat uration of immature oocytes in vitro with follicular fluid results in similar maturation and fertilization rates as for control incubation. Immature oocytes thus retrieved contribute to the overall pregnancy su ccess of unstimulated IVF cycles. It may be better to retrieve immatur e oocytes during unstimulated cycles than during the follicular phase of natural cycles. (Fertil Steril(R) 1998;70:647-50. (C) 1998 by Ameri can Society for Reproductive Medicine.).