Is it better cryopreservation of the ovarian cortex than freezing ova?

What is cryopreservation of the ovarian cortex?

Cryopreservation in the field of assisted reproduction treatment has clearly been a revolution on all levels. It has changed strategies in cases in which fertility has been compromised for any one of a number of reasons.

This revolution began with freezing both male and female gametes over the course of the latter half of the last century. The aim when freezing gametes consisted of preserving fertility if fertility was going to be compromised for any number of reasons, whether these were social or due to illness. In the case of the latter, the main reason was cancer.

When should this type of treatment be used?

Cryopreservation of the ovarian cortex (COC) followed by a transplant has generated general interest over the last few years as a strategy for preserving fertility both for patients who wish to postpone conception and for patients who have to undergo antineoplastic treatment. In fact, as a result of the effect that chemotherapy products have on our organism, it has been observed that around 42% of women (both prepubertal and young women) later develop premature ovarian failure (POF) before 30 years of age.

In many cases, COC followed by a transplant has managed to reverse POF and recuperate gonad functionality from a fertility point of view and also in terms of production of female hormones that avoid premature menopause.

How is the ovarian cortex cryopreserved?

COC begins with surgery using laparoscopy which takes no longer than twenty minutes. During this surgery, small biopsies of the patient’s ovarian cortex are taken. This is where the largest quantity of primordial follicles are located and these give rise to the oocytes. Following this, this ovarian tissue is frozen in compliance with specific protocols until the decision is taken to defrost it so that it can be transferred to the ovary which then recuperates its function.

We currently know that vitrification is a better technique than slow freezing in COC and, furthermore, freezing fragments of the ovarian cortex over one millimetre thick is not advisable.

What are the advantages of cryopreserving the ovarian cortex?

The main advantage of cryopreservation of the ovarian cortex in comparison with freezing oocytes is that it does not entail ovarian stimulation beforehand and, as such, it is a good alternative when patients have hormone-dependant cancer and chemotherapy cannot be delayed.