In vitro maturation (IVM) of immature oocytes for infertile patients is an attractive treatment. It can avoid side effects of ovarian stimulation with gonadotropins. However, at the present the successful results of IVM treatment are lower than conventional in vitro fertilization (IVF) treatment. The key issue may be the IVM medium for immature oocyte maturation. In the present study, we compared 20% (v/v) human follicular fluid (hFF) and 20% (v/v) human umbilical cord serum (hUS) as a supplement to IVM medium. A total of 47 patients with polycystic ovary syndrome (PCOS) underwent 47 IVM treatment cycles. Immature oocytes (349) collected from 32 patients were cultured in IVM medium supplemented with hFF, and immature oocytes (160) collected from 15 patients were culture in IVM medium supplemented with hUS. The results indicate that the final maturation rate of oocytes cultured in IVM medium supplemented with hUS (93.8%) is significantly higher than those cultured in IVM medium supplemented with hFF (77.1%). The percentage of high-quality embryos produced from IVM medium supplemented with hUS (50.0%) is significantly higher than IVM medium supplemented with hFF (23.8%). In addition, the results also indicate that the final maturation rate of oocytes is higher in IVM medium supplemented with hUS and the time course of oocyte maturation is hastened. Following transfer 6 out of 15 patients (40.0%) become pregnant when IVM medium was supplemented with hUS, and 7 out of 31 patients (22.6%) were pregnant when IVM medium was supplemented with hFF. These results suggest that IVM medium containing hUS appears to be a more effective means to stimulate in vitro oocyte maturation and is capable of achieving a promising clinical outcome.