Oocyte cryopreservation: advances and drawbacks.

The field of oocyte cryopreservation (OC) had advanced dramatically since the first reported birth from cryopreserved oocytes in 1986, with a significant increase in pregnancy rates described over the past 5 years due to improvements in vitrification technology, a cryopreservation method which virtually means to achieve a "glass-like" state through avoidance of ice formation. The potential clinical benefits of achieving efficient OC protocols have long been recognized. Specifically, OC can be offered to women who face fertility-threatening situations such as therapy for cancer or rheumatologic disease, premature ovarian insufficiency, or need for ovarian surgery as a measure to preserve fertility. Moreover, many women who plan to delay childbearing are interested in pursuing OC in order to protect against age-related fertility decline. For infertility practices, efficient OC technology stands to dramatically streamline donor egg programs, and is a helpful adjuvant in situations where sperm is unexpectedly unavailable at the time of egg retrieval and for couples who do not wish to cryopreserve supernumerary embryos created from in vitro fertilization for moral / ethical reasons. This review will describe the history of OC technology over the past three decades, discuss clinical circumstances for its implementation, and address areas where more research is needed. Given the remarkable improvements in pregnancy rates witnessed over the past five years, OC is certain to play a much larger role in reproductive medicine over the coming decades.