The method is particularly useful and effective due to the very encouraging results, both for the survival of cryopreserved oocytes after thawing and for fertilisation.
Women whose fertility is threatened (e.g. cancer) and those who deferred childbearing for social reasons (career, finding a partner), can now safely proceed with the cryopreservation of their oocytes.
In 1986, Chen et al. announced the birth of the first child following the cryopreservation of oocytes. This achievement was an important milestone in the area of assisted reproductive technology and cryobiology. Soon, however, the initial optimistic announcements were followed by concerns, as every attempt of the scientists to repeat the method failed. These attempts were marked by particularly low survival rates and even lower success rates. The difficulties were associated with the particular nature of the egg, and since they could not be overcome, the process of the cryopreservation of oocytes did not initially find clinical application.
Almost simultaneously, embryo and sperm cryopreservation made significant progress, seeing clinical application with very positive results. There remained however, a strong need to find a way of maintaining female fertility, especially in young childless women, who face a high probability of loss or significant reduction of their reproductive capacity.
These pressures have prompted scientists to explore new methods of cryopreservation. Of the numerous experimental schedules that were tested, vitrification seemed to be the most appropriate and effective for the cryopreservation of oocytes. Successive modifications to the method led to increasingly improved results.
Today, oocyte cryopreservation is an attainable goal, and therefore enables the maintenance of female fertility. Scientific data indicate that over 95% of oocytes entering the process of cryopreservation survive after thawing and can be safely used in fertilisation, achieving fertilisation rates equivalent to those of fresh oocytes.
Who can benefit?
• When a malignant disease is diagnosed. The highly significant developments in terms of early diagnosis and treatment of cancer have considerably improved prognosis and survival in women. Despite developments in survival rates, the treatments used (chemotherapy – radiation) place too much stress on the reproductive capacity of these women. They often face the possibility of not being able to have children after a treatment of the disease. Developments in the field of cryobiology offer the possibility of preserving their fertility.
• When postponing having children, e.g. in an effort to ensure professional independence. It has been scientifically proven that female fertility decreases at the age of 35 and even more at the age of 40. The decline in fertility in the majority of cases relates to the poor quality of the oocytes. Therefore, the possibility of oocyte cryopreservation at an age when fertility is high relieves women of the pressure of age and suitable choice of partner.
• When having a family history of early menopause. These women usually have small egg reserves in their ovaries and face an early loss of fertility. If these women cryopreserve their oocytes promptly, premature menopause will not affect their ability to become mothers.
• When, for personal moral reasons, either their own or their partners’, do not want to cryopreserve embryos or produce supernumerary embryos. These couples can turn to the egg cryopreservation programme. In this way, they are able to preserve their precious oocytes without undermining their moral viewpoint. At the same time, they have the opportunity of repeating the attempt without the need for the female partner to undergo stimulation treatments again.