OBJECTIVETo investigate the influence of different cycles, ovarian follicle size and IVM culture media on the number of retrieved immature oocytes, maturation rate, fertilization rate, embryo quality and implantation rate, pregnancy rate, delivery rate, survival and development of frozen-thawed embryos from IVM.

METHODSThe oocytes were obtained by follicular aspiration from 19 women undergoing oocyte retrieval for in vitro maturation due to the possible risk of ovarian hyperstimulation in IVF-ET program. One patient was in natural cycle, four patients were in ovulation induction cycles with gonadotropine and fourteen patients is controlled ovarian stimulated cycles. All the oocytes retrieved from follicles with 10.0 - 13.5 mm in maximumdiameter were allowed to culture in medium M-199 (TCM 199) or HTF supplemented with other substance.

RESULTWhen there were nonuniform diameters of follicles and the diameter of largest oocyte exceeded 12 mm, the retrieval rate of oocytes, fertilization rate, and the number of high-quality embryos decreased. The high-quality embryos formation rate was higher for the oocytes cultured in TCM 199 medium than in HTF medium (P<0.01). After being frozen-thawed, the IVM embryos could achieve the same outcome when compared with the conventional IVF treatment. In addition, the offspring were healthy.

CONCLUSIONWhen the nonuniform diameters of follicles and the diameter of largest oocyte exceeds 12 mm,the retrieval rate of oocytes, fertilization rate, and the number of high-quality embryos decreased. TCM199-based medium is better to improve the developmental potential and implantation rate of embryos derived from in vitro matured oocytes. After being frozen-thawed, the IVM embryos could achieve the same outcome when compared with the conventional IVF treatment. In addition, the offspring are healthy.