Egg banking – embryologist perspective

In this webinar, Rocío López, Embryologist at PreGen (Vistahermosa UR), Alicante, Spain, discussed egg banking from her perspective as an embryologist. Egg banking can be defined as a tank or container filled with liquid nitrogen where the oocytes will be stored once they are vitrified. They are found at -196 degrees, maintaining the vitrification properties intact over time. In assisted reproduction laboratories, embryologists work daily with the use of storage banks, they can be used to store oocytes, embryos or seminal samples. This is because the way to preserve gametes or embryos is through the use of current vitrification protocols that allow ice crystals not to form during the process. That increases the survival rates to around 85% and increases ratings of oocyte fertilization similar to when the process is carried out.

Fertility preservation – the indications

The first indication to preserve fertility will be divided into two parts. The first one will be a medical indication, for example, in women who suffer from an oncologic pathology and have to undergo some chemotherapy or radiotherapy treatment since this type of treatment can damage the normal activity of the ovary. Another medical indication will be for patients with signs of autoimmune disease, and also in patients with PCOS (Polycystic Ovary Syndrome), as in some cases, the quality of the oocytes may be affected. In cases of patients with endometriosis, with adhesions of endometrial tissue, they can cause loss of oocyte quality or even cause a decrease in the patient’s ovarian reserve. In addition to medical causes, there are social causes, one of the most common is that women more often want to postpone their motherhood nowadays. In the past, the average age of the first pregnancy was around 22 years old, now, it is 36- 38 years old. Women, during their most fertile years, typically focus on studies, their careers and creating a professional future. Another cause of postponing motherhood is related to a lack of stability at work or not having a partner. Women are born with a specific number of eggs, and their ovarian reserve is an indicator of the number of eggs that a woman’s ovaries contain. This ovarian’s results gradually decrease with each menstruation as the woman ages. In addition, the quality of the eggs also decreases over time. Advancing age can also cause alterations in the oocyte’s genetics and subsequently increase genetically abnormal embryos. Therefore, it is crucial to raise awareness of fertility preservation and inform about available options.

Egg donation

In some cases, it is necessary to use donor eggs, the indications for egg donation are as follows:

• women over 40 years because their ovarian reserves are usually low, and they have a greater alteration in the genetics of their oocytes
• premature ovarian failure; women with AMH hormone levels below normal limits; it can sometimes be linked to a genetic disorder (Turner syndrome, Fragile X syndrome, etc.) or it can also be caused by autoimmune disorders
• unsuccessful results have been obtained in more than 3 assisted reproduction treatments using own gametes
• due to repeated abortions caused by a genetic issue (translocations, deletions, and so on)

Donor selection

The first contact with the donor is a personal interview where 3 generations of the potential donor family tree are studied. In addition, a questionnaire is carried out to know their daily habits and possible risk behaviours that may influence the quality of the eggs. Later, the donor will be evaluated on a psychological and clinical level by professionals. Once the first selection is performed, a blood test is done where the biochemical, serological and chromosomal studies of the donor are performed. In Spain, the egg donation process is completely anonymous, and the matching of a donor with a recipient woman is based on phenotype that must be matched, so the donor and recipient need to have similar hair colour, same eye colour, same race and skin colour, compatibility between blood groups and Rh, compatible genetic study. Genetic studies include chromosomal studies by karyotype and the study of the most frequent recessive diseases in the population. In addition, the donor must always be of legal age and have a good psycho-physical state. In the lab at Vistahermos, there is also a computerized tool called Fenomatch, which indicates the percentage of phenotypic similarity between the patient receiving the oocytes and the donor through photographs of them. A woman can become a donor up to 35 years old. In Alicante, there are lots of female students with different phenotypic traits. The egg donation process can be synchronous or asynchronous. Synchronous donations involve synchronization between the cycle of the donor and the recipient. The donor’s and the recipient’s cycles are synchronized. The donor’s stimulation process and endometrial preparation for the recipient occur at the same time. Another way to carry out the donation process is an asynchronous donation. It is done differently, the egg retrieval is carried out to generate embryos when it is more convenient. The embryos are created and then vitrified, or oocytes are vitrified and fertilized is performed later on, embryo transfer can be postponed.

Egg banking – advantages & disadvantages

Egg banking can be a beneficial solution for many reasons, including:

• it’s one of the new ways of managing an egg donation program
• it allows work to be organized in a more comfortable way for the centres by not having to synchronize the donor and the recipients
• it allows having donors of a race that is not usual one in the area where the oocytes are going to be used
• it allows each recipient to be awarded the desired number of oocytes
• it allows storing of the oocytes from young women, to preserve fertility and avoid future reproductive problems

There are also some disadvantages of embryo banking, one of them is that although there is no increase in chromosomal abnormalities or alterations in the development of the embryos from vitrified oocytes, there may be fewer embryos at the blastocyst stage to culture. A solution to this problem could be allocating a minimum of 6 to 8 donor oocytes per recipient, which will increase the chances of having quality embryos and getting closer to the best embryo transfer options.

Conclusions

Oocyte banking is the new way of managing a donation program. It provides us with the tool to preserve fertility, whether for medical or social reasons. The current cryopreservation protocols do not affect the rates of fertilization, development or embryo quality. Published data indicate that there is a very limited difference in results between the use of fresh and vitrified oocytes.