Chapter 24 - Cryopreservation of human oocytes and the evolution of vitrification technology for this purpose

Summary

This chapter considers the evolution of the practical application of cryopreservation technology to achieve consistently acceptable levels of cryosurvival of this highly cryosensitive gamete while retaining its inherent competency. The majority of oocyte freezing applied clinically has been based directly on traditional human embryo cryopreservation protocols. Such protocols utilize a "slow-freeze/rapid-thaw" approach necessitating use of a programmable freezer, and these protocols have produced to date the majority of the approximately 900 offspring worldwide. With regard to vitrification as a means to cryopreserve oocytes, increased speed of cooling, through the use of better designed carriers and protocols that lessen the concentration of cryoprotectant used while hastening exposure and procedure times, has put this technology on the map, and excellent embryo quality can be obtained from vitrified oocytes. To date vitrification as a cryopreservation method has had relatively little practical impact on human assisted reproduction.