To explore the possibility of clinical application of oocyte vitrification.

From July 2011 to May 2016, a total of 15 intracytoplasmic sperm injection (ICSI) cycles with oocytes preserved by vitrification among 13 patients in Reproductive Medicine Center, Northern Jiangsu People′s Hospital were chosen as study subjects, and they were enrolled into frozen oocyte group. And 288 ICSI cycles by fresh oocytes among 252 patients during the same period in the same hospital were chosen as contrast, and they were enrolled into fresh oocyte group. The clinical data of two groups were retrospectively analyzed. And the general clinical data, fertilization rate, embryo quality and clinical pregnancy outcomes between two groups were compared by statistical methods. The study protocol was approved by the Ethical Review Board of Investigation in Human Beings of Northern Jiangsu People′s Hospital. Informed consent was signed by each participant.

①There were no statistical differences between two groups in general clinical data, including age, duration of infertility, body mass index (BMI), number of ICSI oocytes (P>0.05). ②The survival rate of frozen-thawed oocytes in frozen oocyte group was 87.1% (108/124). The rates of cleavage and high-quality embryo in frozen oocyte group both were lower than those in fresh oocyte group, which were 89.0% vs 98.2%, and 35.4% vs 50.7%, respectively, and both the differences were statistically significant (χ²=27.274, P<0.001; χ²=5.871, P=0.016). There were no significant differences between two groups in the rates of normal fertilization and available embryo (P>0.05). ③There was no statistical difference between two groups in the average number of embryos transferred (P=0.822). The rates of embryos implantation and live birth of in vitro fertilization-embryo transfer (IVF-ET) cycles in frozen oocyte group both were statistically lower than those in fresh oocyte group, and both the differences were statistically significant (χ²=5.534, P=0.017; χ²=7.005, P=0.011). While there were no statistical differences between two groups in the rates of clinical pregnancy and abortion of IVF-ET cycles (P>0.05).

Frozen-thawn oocytes vitrification of IVF-ET can obtain a certain clinical pregnancy rate. But vitrification also has negative influences on oocytes, and thus influencing the qualities of embryos and clinical pregnancy outcomes which needs to be improved. As the sample size in this study is relatively small, the effectiveness of oocyte vitrification still needs multi-center, large-sample and randomized control study to confirm.