Egg Freezing | Dr. Hakan Özörnek

Egg Freezing

What is egg freezing?

Egg freezing involves the process of preserving egg cells (oocytes) obtained from a woman's ovaries for future use with the aim of having children. For this purpose, hormonal injections are administered starting on the 2nd/3rd day of the menstrual cycle, initiating approximately 10-15 days of ovarian stimulation for egg maturation. The growth of eggs is monitored through 3-4 ultrasound checks. Once the eggs reach sufficient size, a trigger shot is administered, followed by egg retrieval under general anesthesia through vaginal ultrasound guidance approximately 36 hours later. This procedure takes about 15 minutes. The eggs are frozen using the vitrification (rapid freezing) method and stored in liquid nitrogen tanks at -196 degrees Celsius until the individual decides to pursue parenthood. By law, they can be stored for up to 5 years, and with Ministry approval, this period can be extended at the individual's request.

In the last 50 years, freezing techniques have made significant progress. Many techniques, initially experimental and then tested in animals, eventually found application in humans. Successful freezing of reproductive cells began in 1949 with the freezing of sperm cells. In 1972, first mouse embryos and later human embryos were frozen. Freezing human eggs (oocytes) posed challenges and remained unsuccessful for a long time. The first reported pregnancy following oocyte cryopreservation was in 1986; however, routine success in achieving pregnancies through frozen eggs took considerable time.

The main reason for this slow progress is the large size of the oocyte, containing a significant amount of water molecules due to being the largest cell in the body. During the freezing process, the cell volume is crucial. Viruses and bacteria, being much smaller in volume, can be frozen and remain viable without any treatment. The large, round, and fragile nature of the oocyte poses many difficulties during the freezing process. The water molecules inside it can crystallize, causing cell damage. In contrast, sperm, being small, can be easily and effectively frozen. Additionally, while a man can produce millions of sperm cells throughout his life starting from puberty, a woman's body produces only 1 or 2 eggs in a 28-day cycle, and she has a reproductive window of 15-20 years.

When 50% of an embryo's cells are lost, the remaining cells can continue to live, sustaining embryo viability and potentially resulting in pregnancy. However, this chance does not exist in oocyte freezing.

Who can freeze eggs?

Initially, the Ministry of Health granted permission for egg freezing only to patients undergoing serious surgical procedures or cancer treatments. However, recent legal amendments now grant all women with low egg reserves or at risk of early menopause the "right to freeze their eggs."

Young, married, single women with low egg reserves can freeze their eggs to have the chance to become mothers whenever they wish. By law, the storage period for eggs is limited to 5 years, but with Ministry approval, this period can be extended at the individual's request.

Egg freezing is performed in the following cases:

  • Before undergoing treatments that may harm egg cells, such as chemotherapy and radiotherapy.
  • Before surgeries leading to the loss of reproductive functions, such as the removal of ovaries.
  • In women with a family history of early menopause or low egg reserve who have not experienced pregnancy yet.
  • In cases where surgery or chemotherapy due to a cancer diagnosis will result in the loss of reproductive ability in women.

Egg freezing can also be considered in the following situations:

  • In patients where no sperm cells are found in the partner on the day of egg retrieval.
  • In countries where embryo freezing is prohibited.
  • In women around the world who wish to delay pregnancy and become mothers at an advanced age.

How are eggs frozen?

The hormonal treatment applied in in vitro fertilization (IVF) is also used in the egg freezing process. The treatment starts with the patient's menstrual cycle, and hormonal injections are administered to increase the number of oocytes. The process and monitoring using ultrasound checks are similar to IVF. During egg freezing, oocytes are collected under anesthesia through vaginal retrieval. Identified under a microscope in the embryology laboratory, the oocytes are placed in special solutions and stored in an "incubator," a specific device. Two hours after the collection process, the cells around the oocytes are removed, and their quality and maturity levels are evaluated. Only high-quality and mature oocytes are frozen and stored in liquid nitrogen at -196°C.

Vitrification Technique

When the vitrification method was developed for oocyte cryopreservation, clinics were able to routinely freeze oocytes. Vitrification, also known as rapid freezing or glass transition, involves passing oocytes through solutions of various densities, placing them on a carrier labeled with the patient's name and code, dipping them into liquid nitrogen at -196°C, and then transferring them to a storage tank. The carrier also bears each patient's national identification number.

Egg Freezing Techniques

In the past, oocytes were frozen using the slow freezing technique, where oocytes were placed in a device after preparation, and a gradual decrease in temperature was achieved. Any problem with the device during this process resulted in the loss of all samples. Vitrification does not require the use of any device. This technique, known as "slow freezing," is definitely less effective than vitrification. Studies have shown that the results of patients using oocytes frozen with vitrification are similar to those using fresh oocytes.

Importance of the Laboratory in Egg Freezing

In vitrification, the experience and technique of the embryologist who freezes the oocyte are crucial. The smallest mistake or delay during the freezing process can lead to the loss of oocyte viability. The oocyte must be placed in the carrier in a very small volume, and the embryologist must perform this under the microscope within a certain time frame. If the volume is too large or the loading time is prolonged, the oocyte loses its viability.

Significance of Egg Freezing

It is not the aging of the uterus but the aging of the egg that makes getting pregnant difficult. The frozen eggs of a 30-year-old woman remain the same at the age of 40. Therefore, the aging of the uterus does not prevent the fertilization process. The egg needs to stay young for fertilization. As age progresses, especially after the age of 35, the number and quality of follicles decrease. After the age of 40, this process accelerates. A woman with a diminishing ovarian (egg) reserve has a reduced chance of getting pregnant, either spontaneously or with treatment, and even if pregnancy occurs, the risk of miscarriage increases. Egg freezing performed early, especially before the age of 35, preserves your "egg reserve," increasing the chance of pregnancy with high-quality eggs.

Choosing the Right Center for Egg Freezing

For a center to provide egg freezing services, having a technologically advanced embryology laboratory and an experienced, competent team is crucial for the proper implementation of egg freezing. The success of the vitrification technique depends on a competent and experienced team. The success of not only the rapid and accurate freezing of your eggs but also their rapid and accurate thawing depends on the laboratory's success. In women at risk of early menopause or with low ovarian reserves, the number and quality of eggs obtained

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