Hessam Roustaei - Novin Infertility Treatment Center, Mashhad, Iran.
Mahnaz Mansouri Torshizi - Novin Infertility Treatment Center, Mashhad, Iran.
Amin Karachian Mohammad - Mashhad University of Sciences, Mashhad, Iran
Mahla Fadavi Islam - Novin Infertility Treatment Center, Mashhad, Iran.

Background: Extensive studies have been performed on in vitro maturation (IVM) of immature oocytes in stimulated or unstimulated cycles. In unstimulated cycles there is no external gonadotrophin administration, which might be beneficial for avoiding ovarian hyperstimulation syndrome (OHSS). In stimulation cycles, we can use IVM to improve fertilization rate and number of embryos especially in poor responders.Methods: This retrospective clinical trial that performed at Novin Infertility Treatment Center included 26 IVM in unstimulated cycles and 51 IVM in stimulated cycles matched for age, and duration and cause of infertility. Immature oocytes in both groups were cultured for 24-30 hours. Oocytes that released first polar bodies were injected by sperm. The rates of maturation, fertilization and cleavage were statistically compared. Result: In unstimulated cycles, 146 GV oocytes were collected, 77 fertilized oocytes(77.49%) and 53 embryos (68.83%) were obtained from 102 mature oocytes(69.86%).In stimulated cycles , 264 GV oocytes were collected, 119 fertilized oocytes(69.59%) and 96 embryos (56.14%) were obtained from 171 mature oocytes(64.77%). There were no significant differences between the two groups for these events but embryo quality was significantly higher in unstimulated group (p≤0.05).Conclusion: These results suggest that oocytes reaching metaphase II in unstimulated IVM programme have better embryonic developmental competence.

Fertilization rate, Stimulated cycles, Unstimulated cycles, In vitro maturation