Egg freezing: definition and procedure

Egg freezing, or oocyte cryopreservation, is a fertility preservation option to increase the patient’s chances of pregnancy at a later age. The first birth from a frozen oocyte was performed in 1986 and involves controlled ovarian stimulation and then egg retrieval (Nasab et al. 2020; Gale et al. 2020). This procedure was an established method for medical reasons like cancer, but elective egg freezing (also called social egg freezing) is a more recent concept. Mainly due to social reasons, such as career pursuits, lack of a partner, or financial stability, the birth rate of women in their 20s has decreased in the last decades, but increased for women in their 30s and 40s (Nasab et al. 2020).

The process takes about 10 to 14 days and consists of first the ovarian reserve testing through an ultrasound and blood tests, to predict the number of retrievable eggs. Around 14 mature eggs are needed for an 80% chance of future live birth in patients with 35 years old or less. In older patients, more eggs are required (Gale et al. 2020). The process consists of ovarian stimulation with medications and ultrasound monitoring during 8-12 days. The egg’s harvest is performed two days later, through an ultrasound-guided transvaginal needle aspiration that lasts between 5 to 10 minutes, but requires 1 to 2 days of rest. The eggs can then be stored for up to 14 years. When the patient wants to use them, the eggs are thawed to undergo in vitro fertilization (Gale et al. 2020).

The risks of egg freezing are related to ovarian stimulation (ovarian hyperstimulation syndrome), infection, and bleeding associated with the egg retrieval procedure. There are two principal types of cryopreservation: slow-freezing and vitrification. Slow-freezing involves decreasing the temperature by approximately ~1°C/min to preserve the cell’s integrity, while vitrification is made with liquid nitrogen. Several studies have shown that vitrification is superior to slow-freezing for cryopreservation of both human oocytes and embryos (Rienzi et al., 2017). It has to be taken into account that egg freezing cannot guarantee a pregnancy since there is still the possibility of unsuccessful embryo transfers (Jones et al., 2019). The clinical pregnancy rates are estimated between 4 to 12% per oocyte. The age of the woman when she went through the egg freezing procedure, and the number of available eggs are the most important factors that determine the probability of a live birth (University of California, nd). Moreover, the age-related obstetric complications remain and the procedure can be very expensive, depending on the insurance coverage (Jones et al., 2019). Oocyte cryopreservation is a very interesting medical technique that is becoming more and more popular, reflecting the need to closely monitor the outcomes, as well as being well informed about the pros and cons of the procedure.

Reference:

Gale, J., Clancy, A. A., & Claman, P. (2020). Elective egg freezing for age-related fertility decline. CMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne, 192(6), E142. https://doi.org/10.1503/cmaj.191191

Jones, B., Kasaven, L., L’Heveder, A., Jaimbrant, M., Green, J., Makki, M., Odia, R., Morris, G., Bracewell Milnes, T., Saso, S., Serhal, P. & Nagi J. (2020). Perceptions, outcomes, and regret following social egg freezing in the UK; a cross-sectional survey. Acta Obstetricia et Gynecologica Scandinavia , 99(3):324-332. https://doi.org/10.1111/aogs.13763

Nasab, S., Ulin, L., Nkele, C., Shah, J., Abdallah, M. E., & Sibai, B. M. (2020). Elective egg freezing: what is the vision of women around the globe?. Future science OA, 6(5), FSO468. https://doi.org/10.2144/fsoa-2019-0068

Rienzi, L., Gracia, C., Maggiulli, R., LaBarbera, A. R., Kaser, D. J., Ubaldi, F. M., Vanderpoel, S., & Racowsky, C. (2017). Oocyte, embryo and blastocyst cryopreservation in ART: systematic review and meta-analysis comparing slow-freezing versus vitrification to produce evidence for the development of global guidance. Human reproduction update, 23(2), 139–155. https://doi.org/10.1093/humupd/dmw038

University of California Los Angeles. Egg freezing. Accessed on 11 Oct 2021 from: https://www.uclahealth.org/obgyn/egg-freezing