Oocyte cryopreservation: where are we now?

Introduction: Since the first live birth from oocyte cryopreservation three decades ago, oocyte cryopreservation has become an important component of ART. Cryopreservation techniques have evolved, leading to higher success rates and the introduction of oocyte cryopreservation into IVF clinics worldwide. Concurrently, there has been an increase in patient demand, especially for so-called 'social egg freezing' that allows women to preserve their fertility in anticipation of age-related fertility decline. This review addresses a need to evaluate the current status of oocyte cryopreservation. It explores current techniques and success rates, clinical applications, the rise of elective oocyte cryopreservation, and future implications.

Methods: A search was performed using Web of Science and PubMed databases for publications between January 1980 and December 2015. Keywords used included 'egg freezing', 'oocyte freezing', 'oocyte cryopreservation', 'oocyte vitrification', and 'fertility preservation'.

Results: The success rate of oocyte cryopreservation has risen, and the increasing use of vitrification offers has improved outcomes, with IVF pregnancy rates now similar to those achieved with fresh oocytes. There are conflicting opinions about the comparative success rates of open and closed vitrification. Patients are accessing and receiving oocyte cryopreservation for a wide range of indications, and there has been a marked increase in patient numbers and oocyte cryopreservation cycles. Oocyte cryopreservation for circumventing age-related infertility is becoming more widely accepted.

Conclusion: Oocyte cryopreservation is an established component of ART, with vitrification now being the cryopreservation technique of choice. Increasing numbers of women undergo oocyte cryopreservation for both medical and social reasons. It is important to continue auditing outcomes and reporting long-term follow-up of children born from frozen-thawed oocytes.