Egg freezing(oocyte cryopreservation - oocyte freezing) is a fertility preservation method used to increase a woman's chances of having a baby.
Egg freezing in Istanbul is a method that women who are currently unable or at risk of becoming pregnant, women who want to become mothers in the future, or women whose ovarian reserve is gradually decreasing, can resort to.
Egg freezing involves collecting eggs from women, freezing them, and storing them to be used later when they are ready to become mothers.
When the eggs are frozen, the quality and "biological structure, i.e., youth, of the age at which they were frozen" are preserved.
Women can benefit from these frozen eggs when they are in their most fertile years, allowing them to become mothers in later years.
Initially, egg freezing was only possible for patients who would undergo cancer treatments. However, with the regulation published by the Ministry of Health in 2014 (Official Gazette No: 29135, 30.09.2014),legal arrangements were made to allow women with low ovarian reserves, regardless of their marital status, to freeze and store their ovarian tissue and eggs. According to this regulation:
These conditions can be documented with a health board report consisting of three specialist doctors, allowing women to freeze and store their ovarian tissue and eggs.
Every woman is born with a certain number of eggs, and during her reproductive years, this reserve decreases at a certain rate with each menstrual cycle. After the age of 35, ovarian reserve and the chance of becoming pregnant naturally gradually decrease.
In addition to the natural decrease in ovarian reserve with age, some medical reasons can cause a decrease in egg reserve or damage to ovarian tissue in young women. Medical causes of ovarian insufficiency include:
Although these women have a low number of eggs, their eggs are of high quality due to their young age. When these eggs are frozen, even if the woman ages, the eggs remain young, and when thawed, the chances of achieving pregnancy through IVF and having healthy babies are higher.
Women delay pregnancy for reasons such as completing their education, gaining economic independence, ensuring appropriate financial conditions, wanting a suitable partner, or not being ready for a second pregnancy.
While the chances of becoming pregnant are highest around the age of 25, this chance decreases gradually into the 30s and drops significantly after the age of 35. The chances of pregnancy decrease further in the 40s, and at 45, it becomes nearly impossible.
With age, the quality of eggs decreases, and chromosomally abnormal eggs are produced. Pregnancies with abnormal eggs can result in miscarriage or babies born with disabilities.
For healthy pregnancies and the birth of healthy babies, it is more successful for egg freezing procedures to be performed under the age of 38. Women are advised not to delay freezing their eggs until later years.
After the initial evaluation of the person who will freeze their eggs in Istanbul, hormone injections are started on the 2nd or 3rd day of the menstrual cycle to stimulate the ovaries to develop multiple eggs, ensuring that a large number of eggs are produced in the ovaries.
With ultrasonography and hormone level monitoring, when the desired response is achieved, eggs are collected under ultrasound guidance using a special needle. The collected eggs are kept in special chemical solutions and frozen using the vitrification method, and stored in tanks containing liquid nitrogen at -196°C.
The egg freezing process consists of 4 stages:
The following are questioned during the evaluation:
On the 2nd day of the menstrual bleeding, daily hormone injections are started to stimulate the ovaries and ensure the growth of multiple eggs. The growth of the small cystic structures called follicles that contain the eggs is monitored with ultrasound.
When the follicles reach a size of 17-20 mm, a final maturation injection of human chorionic gonadotropin (hCG) is administered. hCG acts like the natural LH hormone and triggers ovulation. The ovarian stimulation process lasts about 10-12 days.
Egg collection (OPU) is performed approximately 35-36 hours after the hCG injection under vaginal ultrasonography, which is easy and comfortable. The patient is placed in the gynecological examination position under mild anesthesia and covered with a sterile sheet. An ultrasound probe is placed into the vagina.
The mature follicles in the ovaries are punctured with a needle, and the eggs are aspirated with a suction device. All follicular fluid is collected and sent to the embryology laboratory. The OPU process lasts about 5-10 minutes. After the procedure, the patient is taken to her room to rest for a while. The number of eggs collected may vary depending on age, history, ovarian reserve, and the response to medications.
During the freezing process, cryoprotectants are used to prevent the formation of ice crystals.
Freezing methods:
Slow Freezing Method: This is the traditional freezing method. The concentration of cryoprotectants is low, and the cooling rate is very slow to prevent ice crystallization. In this method, cryoprotectants are used at low concentrations initially. As the temperature gradually decreases and the metabolic rates of the eggs decrease, higher concentrations of cryoprotectants are used. Frozen eggs are stored in liquid nitrogen tanks at -196°C.
Vitrification: This is an ultra-fast freezing method. In this method, cryoprotectants are added in high concentrations to the eggs when they are at room temperature. High concentrations of cryoprotectants are used to rapidly cool the eggs, preventing the formation of intracellular ice crystals. To achieve these rapid cooling rates, the oocytes are placed in small volumes of cryoprotectants and directly immersed in liquid nitrogen at -196°C. This method prevents the formation of ice crystals that could damage the cells or tissues. After freezing, the eggs are transferred to long-term storage tanks for preservation.
Egg freezing in single women is performed using vaginal ultrasonography. The patient is placed in a gynecological examination position under light anesthesia, and under ultrasound guidance, a needle is inserted into the mature follicles in the ovaries to aspirate the eggs, which are then sent to the laboratory.
In women who do not want to lose their virginity, eggs can be collected transabdominally via ultrasound, but this method is not commonly preferred due to the higher risk of organ injury.
The egg collection process is done vaginally. If the structure of the hymen does not allow the ultrasound device to enter, the hymen may be disrupted.
There is no specific storage time for frozen eggs, but if the storage period exceeds one year, the patient is required to submit a signed petition every year, expressing her intention to continue storing the eggs.
If no petition is submitted, the frozen eggs will be destroyed by a commission established by the Ministry of Health. Frozen eggs are typically stored in centers for a maximum of five years. Storage for more than five years requires the approval of the Ministry.
The success rate of egg freezing is largely determined by the woman's age at the time of freezing. For women over 35, the success rates are lower, and the likelihood of success decreases as age increases.
Vitrification is a newer method for egg freezing, and it is still too early to give exact figures about the success rates in terms of freezing, thawing, fertilization, and pregnancy outcomes.
We can estimate the success rate of egg freezing as follows:
Risks Related to the Medications Used in the Treatment
In the ovarian stimulation part of in vitro fertilization, hormone injections are used to stimulate the ovaries to develop multiple eggs. The short-term risks of in vitro fertilization are usually related to side effects from the medications. These medications can cause side effects in a small number of women, but these side effects are typically mild. They include:
Risks Related to the Egg Collection Procedure
Egg collection is a small surgical procedure performed under anesthesia, typically lasting 10-15 minutes. It is done on an outpatient basis, and the woman usually goes home a few hours after the procedure. Both the surgery and anesthesia carry potential risks, but the complication rate is very low.
Egg collection can rarely lead to vaginal bleeding, intra-abdominal bleeding, bowel injuries, peritonitis or inflammation of the peritoneum, and other issues. The needle used for egg collection can also cause bleeding or injury in the intestines, bladder, or blood vessels, leading to infection or damage.
Risks Associated with General Anesthesia
While rare, risks related to anesthesia can occur during the egg collection procedure.
When pregnancy is desired, frozen eggs are thawed and fertilized with sperm from a male partner (using microinjection-ICSI). The resulting embryos are transferred into the woman’s uterus, and pregnancy is achieved.
Studies conducted so far on the health of children born through in vitro fertilization show that there is no additional risk of birth defects for babies born from frozen eggs.
When comparing live births from frozen eggs with those from fresh eggs, no significant differences are observed in pregnancy outcomes (such as diabetes, hypertension, preterm birth, anemia, etc.).
Egg freezing in Istanbul does not harm the baby. However, more research is needed to confirm the safety of egg freezing.
The miscarriage risk in pregnancies resulting from frozen eggs is the same as the risk associated with the age at which the eggs were frozen.
During the egg freezing process, cellular movement and metabolism are stopped. With vitrification freezing technology, the formation of intracellular ice crystals is prevented, allowing the eggs to remain viable in liquid nitrogen for years. Freezing the eggs does not harm the cells, and it does not cause cell death.
The number of eggs that can be stored depends on the woman’s age. In younger women, typically 7 out of 10 eggs will survive the freezing and thawing process. The chance of a live birth from these 7 eggs depends on the woman’s age at the time of freezing and is between 25-30%. Therefore, around 30-40 eggs should be stored to increase the chances of a live birth.
To obtain a sufficient number of mature eggs for freezing, a woman may need to undergo 2-5 treatment cycles. However, freezing a large number of eggs does not guarantee a live birth.
Other factors that may affect pregnancy should also be considered when trying to get pregnant, such as the number of eggs stored, their health, and the age at which they were frozen.
Prof. Dr. Nilgün TurhanGynecology, Obstetrics and IVF Treatment Specialist
PROF. DR. NILGÜN TURHAN
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