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Embryo Freezing

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Embryo Freezing

What is it?

Embryo Freezing is a medical procedure that will preserve a woman’s healthy embryos for using it at a later time.
These frozen embryos will be stored and can be used for the following purposes:

  • To help facilitate a future pregnancy, either for self or donate to other couples.
  • For medical research.
  • For training purposes.

The embryo freezing process usually begins by stimulating the production of potentially fertile eggs by using hormones and other medications. Then these eggs are extracted from the donor’s ovaries for either being fertilized in a lab. After fertilization, these embryos will be preserved through freezing.

Who needs them?

Embryo freezing might be beneficial for female patients facing the following,

  • Genetic disorders of ovarian sensitivities.
  • About to undergo chemotherapy.
  • Taking medications affecting fertility.
  • Approaching advanced reproductive age.
  • Desire for children at a later age.

The Process

An embryo is usually defined as the human offspring right from the second week of its fertilization to the 8th week. Before beginning the embryo freezing process, embryos that are suitable have to be created first. This is usually done by first harvesting the eggs and then get them fertilized in a lab.


The first step in this process is the harvesting of the eggs, which is done by giving hormones to the female patient to ensure proper ovulation. Then, fertility medications are also given to increase the production of the number of eggs.


The doctor will now extract the eggs from the patient’s ovaries using an ultrasound machine, which will ensure accuracy. Once extracted, the eggs will be frozen or used at once.


The doctor will start the fertilization process using either In Vitro Fertilization (IVF) or Intra-Cytoplasmic Sperm Inejction (ICSI), depending on a combination of factors. The eggs are then exposing them to the sperms, usually in a petri dish and then this mixture is cultured in a laboratory.
The actual process of fertilization might take 16-20 hours and these fertilized eggs are called Embryos.


The development of the embryo is now monitored over the next week. Then a suitable embryo might be used for implantation into the patient’s womb, if the patient wants an immediate pregnancy.

Embryo Freezing

The remaining embryos will then be frozen for later use. This usually done by first getting rid of the water present in these cells as they form crystals when frozen. These crystals will expand, bursting the cell and causing its death.
In order to get rid of this issue, the water in the embryo is replaced with a cryoprotectant, a protective substance. Before these embryos are frozen, they are incubated in rising levels of cryoprotectant.
Once the water content has been removed completely, the embryo is then cooled to their state of preservation by using either of the following methods of embryo freezing:

  • 1)Slow Freezing: helps in protecting the embryos from damage by keeping them in sealed tubes first and then lowering the temperature of the tubes slowly. This prevents the aging of the embryo cells and also from damage. This helps the frozen embryo to last longer than in its fresh state. This process I time-consuming and requires expensive infrastructure.
  • 1) Vitrification: involves freezing the cryoprotected embryos quickly that the water, which remains after cryoprotection, does not get enough time to form ice crystals. This process will help in protecting the embryos and increase their chances of survival during thawing.

Once the embryos are frozen, they are stored in liquid nitrogen so as to use them in the future. The embryos are usually stored in sealed containers at temperatures of -196.1oC. No biological processes can occur at this temperature. These frozen embryos can be kept viable indefinitely. However, some clinics might restrict the time of preservation due to infrastructure problems.

Authored by Dr. Anitha Mani - Infertility Specialist & Laparoscopy Surgeon