What is the procedure for Embryo Cryopreservation?

May 12, 2022
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Planning and making babies comes as naturally to everyone as breathing, walking, eating, and sleeping. The procedure that leads up to pregnancy is also undeniably beautiful, but while having sex, sometimes conception may not be as easy and quick as you may have thought.

To Consult: The Best Fertility Specialist in Chandigarh

At times couples especially women undergo a lot of stress in adding a member to the family. Especially with the current climate of increasing infertility, they get stressed and worried if they fail to conceive in a couple of months after having unprotected sex. Well, to all those ladies hold your horses, since there are advancements in reproductive medicines and technologies that can help you with it. Read further!

What is the Cryopreservation of Embryo?

Embryo cryopreservation or embryo freezing is the process of freezing and storing the extra embryos for future use. Cryopreservation of embryo is often a part of IVF (in-vitro fertilization) programs.

In IVF, embryos are made by fertilizing the eggs with the sperms (in a Petri-plate) in a laboratory condition. All the embryos developed cannot be transferred into the surrogate; hence the extra ones are stored which can be used for a fresh IVF transfer. This storing of embryos is known as cryopreservation of embryos.


Embryo cryopreservation or embryo freezing also gives an additional opportunity for pregnancy, through Frozen Embryo Transfer (FET). This way the women don't have to undergo another ovarian stimulation and retrieval process.

What is the procedure?

Preserving the embryo for later use is the primary objective of embryo freezing. Therefore, the embryo has to be maintained in such an environmental condition that it does not die.

The steps involved in freezing or cryopreservation of the embryo are:

Step one: Embryo Selection

As part of the IVF process, the woman is medically stimulated to make more eggs. The man also gives a higher number of sperm cells. When both are mixed, several embryos often tend to develop. The doctor usually transfers one to four embryos into the woman while the rest is left over. Here, the healthiest embryo or embryos are selected so that it can be stored for future use.

Step two: Removal of the water content

The selected embryo cannot be frozen directly without replacing the water content within the cells. This is because when it is kept for freezing the water content inside the cells also freezes and crystalizes. the crystal formation can cause expansion which can burst the cell open, causing it to die.To prevent this from happening, cryoprotectants are used to replace the water content inside the cells.

Step three: Embryo Freezing

As the water content is removed, the embryo is cooled (20 degree Celsius) and subjected to freezing. This is achieved either by one of the two methods:

  • Slow freezing

In this method, the embryos are put inside a tube (straw sealed with sterilized bearings) to protect it from any damage. Once the embryos are placed inside, the temperature is lowered gradually in the tubes (from 20° to -7° and finally to -35°) to prevent it from aging and any damage. The straw/tube is removed from the freezer and stored in the liquid nitrogen container maintaining a temperature of -196° Celsius.

What is Vitrification of Eggs and how is it done?

This is a very quick process. Here the cryoprotected embryos are frozen at a faster pace where the water molecules present in the embryos don't have enough time to crystallize. After freezing, the embryos are stored in the liquid nitrogen container.

This process is seldom used as it requires a large quality of cryoprotectants and also the liquid nitrogen can pose a risk of contamination.


How can the embryos be used again?

Well, the defreezing process is known as thawing. When embryos are needed, it is taken out from the liquid nitrogen container and placed in the water bath where the temperature is made to rise gradually. As the temperature raises the cryoprotectants leaves the embryos.  To limit the effect of the leaving cryoprotectants, a stepwise dilution process is done.

If you are struggling to get pregnant, it is never too late to turn towards advancing reproductive medicines and technologies for help! You can even consult with your healthcare specialist for more options and information.