Background: The supplementation of human chorionic gonadotropin (hCG) into culture medium in rescue in vitro maturation (r-IVM) has been reported to improve the maturation rates of immature oocytes derived from stimulated cycles. However, the impact of this enrichment on embryo quality is yet to be understood. The purpose of the current study was to investigate the effect of hCG on the embryo quality following r-IVM.
Methods: A total of 152 immature oocytes consisting of germinal vesicles (GV) and metaphase I (MI) were collected and classified into 1) control group (n=73; GV=22, MI=51) cultured in culture medium only, and 2) experimental group (n=79; GV= 23, MI=56) cultured in culture medium supplemented with 0.5 IU hCG. Study parameters were analyzed using Student’s T-test or Kruskal Wallis and chi-square at a 95% confidence level.
Results: After 24 hr, the maturation rate of the control and experimental groups was comparable (57% vs. 70%, p=0.58). Following intracytoplasmic sperm injection (ICSI), the fertilization rate was significantly higher in the experimental group than in the control group (49% vs. 36%; p=0.03). However, the number of good-quality embryos was similar in the groups (16% vs. 6%). 
Conclusion: Our study suggests that hCG supplementation into the culture medium during r-IVM does not affect embryo quality but improves the fertilization rate. Further research is needed to scrutinize the role of hCG in fertilization.