The vitrification of oocytes or embryos is a freezing method which consists in dehydrating the oocytes or embryos with cryoprotective substances to protect them from damage and then submerging them in liquid nitrogen (-196ºC) in small volumes.

How is it done?

The embryos or oocytes are protected with solutions which contain high concentration of cryoprotectors and are then quickly placed in a small drop, hardly bigger than the embryo or oocyte. They are deposited on a device specially designed for this process, called Cryrotop, with the patient’s identification. The Cryrotop is submerged in liquid nitrogen and stored in the Nitrogen Bank.

What does the vitrification process consist of?

The main problem with freezing biological material is that ice crystals can form. Since water expands when it freezes it damages the surrounding tissue unless the water has been eliminated before freezing.

During the vitrification process all of the water from inside the cell is substituted with a cryoprotective solution, which allows the cells to be submerged in nitrogen without forming ice crystals.

Why is it better than the traditional freezing technique and what is the difference?

Since this method uses an increased concentration of cryoprotectants it is more efficient in eliminating water from the cell, giving the embryos or oocytes more protection against the side effects of freezing. The traditional freezing method is slower, and many times the cells aren’t able to be totally dehydrated, putting the embryos and oocytes at risk.

Why does it improve the success rates in ovule programs?

The oocyte vitrification will improve future success rates because, although fresh oocytes and embryos are more likely to be successfully implanted than the frozen ones, the advantage of using frozen eggs is that they are easily available. Using frozen eggs also reduces the waiting period and improves synchronisation between the donor and the recipient.