Vitrification is an ultra-fast freezing process. During the vitrification process, water within the cells is removed by adding certain solutions. This prevents the formation of the ice crystals that destroy cells. Mechanical damage to parts of the cells is a very rare occurrence. The fast rate of cooling allows for the content of the straw to turn into a glass-like substance rather than ice. Avoiding the formation of ice crystals is essential when it comes to thawing the embryos at a later date and in fact, increases the survival rate to over 95%.


There are two types of methods that can be used by embryologists to freeze and preserve oocytes /embryos: Vitrification, a “flash freezing” technique, and slow freezing, an older technique that is, well, exactly what it sounds like.

Here’s How Slow Freezing Works

The cell is cooled very slowly at a decrease of 0.3º–2ºC per minute until it reaches the final storing temperature of -196ºC (or about -321ºF). That’s the temperature required for the frozen oocytes/embryos to be safely preserved.

It ensure all biological processes cease inside the cell. In total, the entire process takes a couple of hours, which is why this technique is termed “slow freezing.” (It’s also sometimes called “controlled-rate” or “slow programmable” freezing.)

In contrast, vitrification is a “flash freezing” method that cools cells so quickly to -196ºC that they become “glass-like” or “vitrified.” While the slow freezing technique takes hours, vitrification is completed in minutes.

However, the huge advantage of vitrification is that it can be used, for example, to preserve non-inseminated egg cells of women who are about to undergo chemotherapy or radiotherapy, which pose a risk to fertility .This approach can also be used to treat the egg cells of women aged between 25 and 35 who would like to make arrangements for Fertility preservation so that they can have an improved chance of pregnancy later on (for example, when they are 40 – 45 years old). This is also known as social freezing.


Both types of cryopreservation are still in use by embryologists today. But here at DPU IVF AND ENDOSCOPY CENTRE, we listen to the science—the many studies that have clearly demonstrated that vitrification is the superior freezing technique with much higher success rates for oocyte/embryo preservation. That’s why vitrification has become the cornerstone of our lab.

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