Oocyte cryopreservation is the process of removing, freezing and storing a woman’s eggs after the ovaries have been stimulated. Eggs are then fertilized when a woman, who is not necessarily the source, is now ready to conceive a child.

Oocyte cryopreservation has been regarded as an alternative for women with different conditions and issues hoping to have children in the future. Knowing how this process works will help you understand why it has become a better option for many women. Here is an overview of how egg freezing works to help preserve a woman’s eggs for future use:

Ovary stimulation

To start the process of oocyte cryopreservation, you will be instructed to undergo a series of follicle stimulating hormone–FSH–injections which can be self-administered daily for one to three weeks. FSH is responsible for stimulating your ovaries to produce more than one egg. While hormones are being injected, your doctor shall regularly monitor your ovaries and conduct blood tests and ultrasounds to make sure your eggs are healthy until they are ready for harvesting.

Egg extraction

When the eggs have matured and are ready for harvesting, you will be given a medication that will set off ovulation. You will be put under mild general anesthesia or sedation for the egg retrieval process, which lasts for about fifteen minutes. An ultrasound-guided needle will be inserted through your vagina to the ovarian follicles to remove the fluid. This fluid now contains the eggs, and the number of eggs depends on how your body responds to the FSH. The fluid is the examined under a microscope to determine the number and condition of eggs it contains.

Egg freezing

Since eggs contain a great amount of water, they are dehydrated during the freezing process using a cryoprotectant solution. Soaking eggs in this solution prevents the formation of ice crystals that may cause the destruction of the egg’s integrity. The freezing process can be conducted by using either a slow-cooling method or a vitrification process.

* The slow-cooling method is a freezing method that involves gradually and slowly freezing the eggs by dropping the temperature by half a degree at a time. Most fertility clinics use the slow freezing method.

* The vitrification process, on the other hand, allows the eggs to freeze faster but requires more cryoprotectants during the freezing process.

At this time, no significant differences have been observed between the two methods of freezing eggs.


These frozen eggs are not limited for use by the owner alone. They can also be donated to other women for assisted reproduction. Once you or the recipient is now ready to conceive, the frozen eggs are then taken from the freezer and thawed out by a fertility specialist who ensures the eggs are properly thawed to avoid flooding that may cause failure of the sperm to fertilize the eggs. Once ready, eggs in great condition undergo a process called intracytoplasmic sperm injection for fertilization. Instead of allowing the sperm to naturally penetrate the egg, the sperm is directly injected to the egg in this process. The fertilized eggs are then set in your uterus using a catheter, expecting at least one egg will result in a successful pregnancy.

Egg freezing, or Oocyte cryopreservation, is particularly helpful for women who want like to preserve their eggs for future pregnancy, for those going through assisted reproduction, and those diagnosed with cancer but who have not started chemotherapy or radiotherapy treatments which are known to destroy eggs.