Clinical application of human oocyte cryopreservation

In recent years, the success of human oocyte cryopreservation has improved dramatically. Currently, there are a couple hundred babies born worldwide with the use of cryopreserved oocytes. The oocyte survival after freezing/thawing process is in the range of 70-95%, comparable to embryo cryopreservation, depending on techniques used. With the change of cryopreservation media to choline-base, the outcome of oocyte cryopreservation has shown to improve. Moreover, new freezing technique, vitrification, has been developed resulting in better survival outcome without the need of sophisticated equipment. Fertilization rate of cryopreserved oocytes with ICSI is approximately 70-90%, comparable to that of fresh oocytes. However, the pregnancy rate varies from 10-40%. The main reason of varying outcome is the difference in technique of cryopreservation. Clinically, oocyte cryopreservation can be applied to preserve fertility of female cancer survivors, to delay childbearing and to quarantine oocytes in oocyte donor program. Oocyte cryopreservation can also be performed as an alternative to embryo cryopreservation due to ethical consideration.