Cryopreserved oocytes: update on clinical applications and success rates

Over the past 3 decades, oocyte cryopreservation procedures have improved rapidly. However, there is limited research reviewing the efficacy of different cooling protocols and inadequate data comparing in vitro fertilization (IVF) outcomes from fresh oocytes with cryopreserved oocytes.

The present review was performed to investigate advances in oocyte cryopreservation technologies and identify areas for further research, to determine whether results from IVF using cryopreserved oocytes are comparable to IVF using fresh oocytes, and to identify the patient populations requiring access to oocyte cryopreservation.

A literature review was conducted. OVID (MEDLINE) and PubMed databases were queried using phrases such as "oocyte or egg" and "cryopreservation," "vitrification," or "slow cooling or slow freezing." A total of 180 studies were selected for review.

Current literature suggests that vitrified oocytes produce superior IVF results to slow-frozen oocytes and may yield comparable outcomes to IVF with fresh oocytes in certain patient populations. Patients at risk of infertility due to disease or age-related decline or oocyte donation programs, couples who fail to produce semen when required for IVF, and patients with legal or ethical reasons against embryo cryopreservation may access cryopreserved oocytes.

We suggest that women who comprise the previously mentioned patient populations should be offered oocyte vitrification technology. Further research is required to confirm IVF success across all patient populations and determine the best cryopreservation protocols.

This review will be relevant to clinicians interested in fertility treatments using cryopreserved oocytes, fertility preservation, oncology and fertility, and immunology and fertility.