Egg freezing (cryopreservation) is an important part of assisted reproductive treatment. application. Obtaining embryos from frozen eggs dates back to the 1980s. Egg There have been significant developments in the freezing process since the 1980s. Slow freezing has replaced vitrification. Vitrification is a safer and more successful procedure. Vitrification is now the gold standard method for oocyte (egg) freezing.
Oocyte freezing can have many purposes. The most common reasons are to protect the eggs of oncology patients from cancer treatment or to delay pregnancy for personal reasons. Oocyte storage can also be used in donation (egg donation) treatments. Pregnancy by egg donation is a widely used treatment method today.
In oocyte donation treatment, the growth of the donor's eggs and the preparation of the recipient mother's uterine wall must be synchronously compatible. When egg donation is performed in Cyprus, especially in our own clinic, we take care to ensure this synchronization. It may not always be possible to achieve this harmony. In this case, we may need to use donor eggs that have already been frozen and stored. Furthermore, thanks to egg storage banking, the egg recipient mother-to-be has more options in selecting eggs and determining the timing of pregnancy.
Current data from around the world indicate that IVF treatments with embryos prepared from frozen eggs have good results. The eggs are exposed to equilibration fluid 3 hours after collection (OPU) and then to vitrification fluid for 30 seconds. Each egg is then removed with a very small volume of vitrification fluid and placed on a thin polypropylene strip attached to a rigid-plastic holder. As soon as the oocyte is placed on this Cryotop strip, it is immersed in liquid nitrogen. It is then placed in a hard plastic container.
For thawing, the protective plastic container is removed from the Cryotope and placed in 37°C thawing solution for 1 minute. The eggs are then soaked in dilution liquid for 3 minutes and washed twice for 5 minutes with washing liquid. The eggs are fertilized by ICSI (injection of sperm into the egg) 3 hours after thawing.
Comparative studies show that fertilization rates of frozen and thawed eggs are lower than fresh eggs. It has also been shown that the morphology (structure) and development of embryos obtained from frozen and thawed eggs are worse than embryos obtained from fresh eggs. Despite these data, there is no statistically significant difference in pregnancy outcomes between treatments with fresh and frozen eggs.
The egg is the largest cell of the human being. The smaller the cells, the easier and safer it is to freeze and store them: As is the case with sperm. Several types of damage occur during egg cryopreservation. During freezing, sensitivity to cooling and cooling solutions, increased permeability of the plasma membrane to protective solutions, and altered tolerance to osmotic swelling are observed.
As a result of the studies, although there is a decrease in fertilization and embryo development results in treatments with frozen eggs, there is no significant decrease in pregnancy rates. Despite this, it is recommended in the current literature to use fresh eggs if possible.
In IVF treatments in Cyprus, we use fresh oocytes in our clinic except for special cases. Based on our own experience, we can say that fresh cycles are more successful. We do not prefer to use frozen eggs especially if PGD procedure is to be performed.
