Thanks to recent developments, it has become possible to freeze eggs. The technique used to do this is called vitrification.
Egg Freezing
Freezing eggs offers women the opportunity to keep their reproductive potential without the necessity of fertilisation first. Women who has excess oocytes retrieved per cycle having the opportunity to freeze their extra eggs for future trials without starting medications and ovum pick up procedure.
When eggs are frozen, their biological clock is put on hold: they don’t continue to age and cannot be damaged by external factors. Preventive storage is therefore an appropriate measure to preserve fertility.
Women: Egg Freezing
General: Before you start with the procedure, one of our consultants will see you and explain the process in detail, listing any possible risks based on your individual circumstances.
Before we start, we ask for a health screening to rule out infectious diseases or other medical conditions.
Procedure: Like in IVF, it involves a series of hormone injections that stimulate the ovaries (ovarian stimulation) to release more mature eggs, followed by ultrasound monitoring and blood test analyses.
The collection of the matured eggs is carried out by a doctor using a needle, guided to the correct area by an ultrasound probe. It is performed under sedation and it does not take longer than 20-30 minutes. After a recovery time, of up to 3 hours, you can return to your daily activities with minimal limitations (for instance, we recommend that you will not drive). During this time, our medical staff will monitor you, checking whether you experience any discomfort. You may be prescribed with a painkiller before being discharged.
With this procedure, a variable number of mature eggs can be isolated. These are washed and dehydrated (water content removal) in preparation for the laboratory freezing. We use the method of vitrification, which is a rapid cryopreservation technique involving liquid nitrogen. The removal of water from the eggs reduces chances of damage by the formation of crystals during the fast freezing process.
Alternative, if you undergoing an egg accumulation process, the freezing of your eggs may be done in stages, depending on how many eggs you may have after a round of ovarian stimulation with natural-cycle, minimal-stimulation or full IVF cycle (based on your circumstances). Once we have reached a given numbers of eggs, they can be thawed for usage.
The eggs can be kept in this stage, in liquid-nitrogen storage, for up to 5 years. The frozen eggs have their ‘biological clock’ suspended, which means that they do not continue to age and cannot be damaged by environmental factors.
Usage: Once you decide that you are ready to use your eggs, they are thawed to normal temperature through a carefully controlled process.
It is highly unlikely that all eggs will survive the freezing-thawing process. The survival rate is around 90-95%, based on individual circumstances.
Depending on the quality of available sperm, the restored eggs can be fertilized either by IVF with or without Intra-Cytoplasmic Sperm Injection (ICSI). The resulting embryos are cultured from 3-5 days, at which point, one or two of the best ones are selected and transferred back to the uterus. Prior embryo transfer in these cases, we recommend assisted hatching to increase chances of implantation. Pregnancy should resume as normally.
Risks from the actual procedure are minimal and well-recovered eggs have a high chance of being fertilized proceeding to a live birth. A recent review* of children born from vitrified eggs found no increased incidence of anomalies or incidents compared to infants conceived naturally or through fresh-egg IVF / ICSI.
The overall limiting factor is the success of the egg freezing-thawing procedure itself, which depending on the case, can result in a low yield. Constant experimental improvements will lead to much higher success rates in the future.
References
* Cobo A, Domingo J, Pérez S, Crespo J, Remohí J, Pellicer A (2008). Vitrification: an effective new approach to oocyte banking and preserving fertility in cancer patients. Clin Transl Oncol. 10(5):268-73. (PMID: 18490243)