Abstract:

Recent advances in vitrification techniques have markedly improved the efficacy of oocyte cryopreservation in terms of oocyte survival and pregnancy as well as live birth rates. However, there is still room for improvement of oocyte vitrification techniques. Remaining challenges include the development of less cytotoxic vitrification solutions and safe vitrification devices. Guided by the principles of cryobiology, it should be noted that the essential element to oocyte survival during the vitrification-thawing procedures is a very high warming rate during thawing. There is no solid evidence to suggest a safety issue when the vitrified oocytes are stored for prolonged periods of time in liquid nitrogen. While recent advances in the efficacy of oocyte vitrification have been positioned by this technology as a standard procedure for female fertility preservation or in the setting of egg donation, long-term follow-up of infants born from this technology remains essential. The research progress of oocyte cryopreservation techniques is reviewed in this paper, including the application and role of vitrification techniques, velocities of freezing and thawing, immature oocyte cryopreservation, oocyte preservation and safety of oocyte cryopreservation.

Key words: oocyte, vitrification freezing, fertility, preservation, pregnancy