Chapter 23 - Oocyte cryopreservation

Summary

Ovarian cryopreservation presents a valid alternative to egg freezing in some circumstances. The possibility to store oocytes for a later use is also an important consideration for women who choose to postpone motherhood for personal or professional reasons. Any newly developed protocol should consider the biochemical and physical properties of the oocyte. In addition to surviving the cryopreservation/warming process, the oocyte needs to maintain competence to fertilize and develop in vitro to the appropriate embryonic stage without any structural alterations. Slow cooling protocol is characterized by a slow decreasing temperature rate. Several mathematical models define an optimal curve applicable to oocytes since the freezing rate is vital to achieve sufficient and progressive dehydration, and thereby minimize the potential of intracellular ice formation. During fresh cycles only a few oocytes can be inseminated; therefore, cryopreservation is the only option to avoid wastage of surplus eggs and consequent repeated ovarian stimulation.