What is egg freezing?
Egg freezing, also known as oocyte cryopreservation, is the process of preserving a woman’s fertility so that she can attempt pregnancy at a later time.
Why is egg freezing used?
Egg freezing is important because women have a finite number of eggs in their lifetime. Which is approximately 1 to 2 million eggs. That amount is decreased to 300000 to 400000 eggs by the time they reach puberty. This number decreases with each passing month from this time. And it is not only the quantity of the eggs but the quality also starts to diminish as the age advances for each woman.
Who is egg freezing for?
- Women who have to delay childbearing for social reasons.
- To preserve fertility for medical reasons like undergoing surgery or cancer treatment.
- Because of ovarian disease that increases the risk of damaging the ovaries.
- In case of family history of premature ovarian failure.
- Ethical or religious reasons that don’t allow freezing of embryos.
- To donate eggs for a known or unknown recipient.
What are the steps for egg freezing?
The following steps are included in the egg freezing cycle:
- Prescribing hormone medications that help grow multiple follicles in order to collect multiple eggs.
- Conducting ultrasound scans and blood tests to check ovarian response.
- Administering trigger hormone injection 34 to 36 hours before retrieving the eggs.
- Using ultrasound guidance and sedation in an operation theater to retrieve eggs from the ovaries.
- The harvested eggs are placed in a plastic dish with some media and left for a while. After that the surrounding cells are removed from the eggs.
- The matured eggs are frozen by vitrification and stored in liquid nitrogen.
Egg freezing FAQs
What is ovarian stimulation?
Ovarian stimulation is usually recommended to collect multiple eggs in most cases. Hormone injections containing follicles stimulating hormone (FSH) are required for the simulation with or without luteinising hormone (LH). These injections are generally started at the very beginning of the menstrual cycle or during an induced bleed. The type of hormone and the dose is specific to each patient. It depends on various factors such as age, body mass index, anti-Mullerian hormone (AMH) levels, antral follicle count (AFC) and response to previous ovarian stimulations if available from your medical history.
You must administer the injections yourself everyday at the same time.
Depending on the ovarian response the injections are to be administered for 10 to 14 days. Your expert consultant will prescribe the trigger injection when your follicles have reached their optimal size to ensure the eggs within your follicles mature and are ready to be harvested 34 to 36 hours later.
How is the stimulation cycle monitored?
Five or six days after taking the hormone injections you will undergo transvaginal scans every 2 or 3 days. This is important as it helps in determining the development of follicles, to alter the dose of the medicines if required to ensure adequate response and to decide when to administer the “trigger” injection for egg retrieval. Sometimes blood tests are also required along with the scans to better understand the response to ovarian stimulation.
How is the egg collection performed?
Egg collection is performed in the operation theater close to the laboratory. Sedation medication will be administered to you through an intravenous line. Nursing staff and an anesthetist will be present with you along with the expert consultant. Pain relief may be given during or after the procedure if required.
Based on the number of follicles and the difficulty to access the ovaries this process can take 15- 30 minutes. The fluid of each follicle is extracted into a clear tube by a fine needle which is inserted through the vagina into the ovaries by sliding into a guide mounted on the transvaginal scan probe. This fluid is then passed to the embryologist who checks for the eggs.
Very rarely, if there is a small area of bleeding, absorbable stitches may be put inside the vagina. Normal activities can be resumed the next day.
How are the eggs frozen?
Once the eggs are retrieved, they are washed and prepared for freezing. The technique used is called vitrification and is only used to freeze mature eggs. Vitrification is preferred over slow freezing in most centers because there is no formation of ice crystals. Thus, there is less risk of damaging the eggs during freezing.
How are the frozen/warmed eggs fertilized when I want to use them?
The frozen eggs are prepared for warming in the laboratory by the embryologist. After warming, the surviving eggs are fertilized with the donor or partner’s sperm using ICSI technique. These fertilized eggs are then kept in the incubator for a few days where they are checked for embryo development and blastocyst formation before performing the embryo transfer.
What is the survival rate of frozen eggs and clinical pregnancy rate?
It has been around 10 years since egg freezing by vitrification is being used. Data present in literature tells us that almost 80% of vitrified eggs will survive. Which is much higher compared to slow freezing as it has a survival rate of 55-65%.
The rate of clinical pregnancy using frozen eggs can depend on many factors like quality of eggs, quality of sperm used for fertilization and the patient’s age when the eggs are frozen. The published reports suggest a 40% rate of clinical pregnancy using frozen/warmed eggs.