Types of Vitrification

Embryo Vitrification

Fertilized eggs are called embryos, in embryo vitrification the eggs and sperm are retrieved from respective individuals and fertilized in the laboratory before vitrification. On fertilization, it may be observed that the resultant embryos are high in quality and quantity and the parents-to-be may choose to freeze the same for future cycles of IVF.

Prior to their freezing, the embryos are put in 5-10 times more cryoprotectant than slow frozen embryos. This causes hardening of the shell surrounding an embryo. This is done such that, when the embryo is thawed and placed in the uterus, it will have to escape from the shell.

Oocyte Vitrification

Oocytes or unfertilized eggs are frozen with the help of high concentrations of cryoprotectants. This is done over multiple steps such that the eggs survive the freezing process and are eventually available for fertilization when required. The eggs are bathed in a series of cryoprotectant solutions with increasing concentration. Eventually, when they are placed in the last cryoprotectant solution, they are instantaneously frozen.

Using Frozen Embryos & Eggs

Using frozen embryos and eggs makes it difficult for patients to opt for a regular IVF cycle as the freezing leads to the hardening of the eggs’ outer membrane. This makes them impenetrable for the sperm and therefore the eggs will need to be fertilized using ICSI, which is a procedure wherein a single sperm is directly injected into the egg. When patients decide to use their vitrified eggs or embryos, they are pulled out of the cryopreserved liquid nitrogen and run through various media solutions to remove the cryoprotectant and rehydrate the cells with water.

Fresh vs. Frozen

While both fresh and frozen embryo transfers have been successful in their own way, depending on the condition of the patient & their needs, doctors prescribe either one of the two modes – overall data suggests that frozen embryo transfers are slightly more successful than fresh ones. However, that alone is not the only parameter to arrive at a decision, as many across the field of fertility continue to debate the issue with vigour.

In the past, before the advent of vitrification the process of freezing the embryo was too slow and too ineffective. It did more harm than good to the embryo and therefore it was an overwhelmingly better choice to go for fresh embryo transfers. However, this has changed considerably now, and it is now possible to freeze the embryo a lot more efficiently and without compromising the quality.

Freezing Unfertilized Eggs

There will always be unfertilized eggs in an IVF cycle, which are now frozen and will require to be thawed before deposition in the womb at a later state. Frozen eggs that had been previously retrieved, can now be used even years earlier. Whenever required, they can be thawed, fertilized, and placed into the uterus.
IVF with Delayed Frozen Embryo Transfer

Embryo transfer is the final stage of the IVF process wherein mature eggs are retrieved from ovaries and fertilized by sperm in a lab. With the vitrification option, patients can now opt for IVF with Delayed Frozen Embryo Transfer, which is essentially giving women time to recover from any negative effects of the stimulation drugs, thereby increasing chances of successful implantation and pregnancy.

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