What is the process of egg freezing?

Dubai, UAE; February 20, 2017:  While sperm and embryos have proven easy to freeze, the egg is the largest cell in the human body and contains a large amount of water – when frozen, ice crystals form that can destroy the cell.  This necessitates dehydrating the egg and replacing the water with an ‘anti-freeze’ prior to freezing, in order to prevent ice crystal formation. This is done using cryoprotectants, which replace most of the water within the cell and inhibit the formation of ice crystals.

Eggs are frozen using either a slow-freeze, slow-cooling method or a newer flash-freezing process known as vitrification. Vitrification requires a higher concentration of cryoprotectants but is much faster and results in a solid, glass-like cell that is free of ice crystals. Freezing is a phase transition, but as opposed to slow-freezing, vitrification is a physical transition. Realising this fundamental difference, the vitrification method has been developed and successfully applied in IVF treatment, with the first live birth following vitrification of oocytes achieved in 1999. Vitrification eliminates ice formation inside and outside of oocytes on cooling, during cryostorage, and on warming. Vitrification is associated with higher survival rates and better development compared to slow cooling when applied to mature oocytes. 

During the freezing process, the zona pellucida (egg membrane) can be modified, preventing fertilisation. When the eggs are thawed, a special fertilisation procedure is then performed by an embryologist, whereby sperm is injected directly into the egg with a needle rather than allowing sperm to penetrate naturally by placing it around the egg in a dish. This injection technique is called Intracytoplasmic Sperm Injection (ICSI) and is used in IVF.

Why would a woman need egg freezing?

1. Those who would like to preserve their fertility until they are ready to start a family. Today, we see many women delaying childbearing due to career and other personal or medical reasons, and then struggling to conceive in later years. Pregnancy rates from frozen eggs will depend on the woman’s age at the time she freezes her eggs, but will not be affected by the age at which she comes back to use them. 

Therefore, the chance of future pregnancy in women older than 38 at the time of freezing is likely to be lower than that seen for younger women. To date, there are few reports of pregnancies in women over 38 from frozen eggs. This is mostly due to lower age cut-offs in egg freezing studies and the relatively low number of women who have come back to use their frozen eggs so far. This is called social freezing. 

2. Those diagnosed with cancer who have not yet begun chemotherapy or radiotherapy. In the short time that is available, stimulation of the ovaries can be undertaken safely and eggs can be preserved. Significant damage to the ovarian follicles can be expected after cancer treatment. 
3. Those with religious or other reasons not to freeze embryos during in vitro fertilisation may find that egg freezing is a viable option. 

When should a woman freeze her eggs?
The simple answer is to pursue egg freezing, or oocyte cryopreservation, in the prime reproductive years — a woman’s 20s and early 30s — to take advantage of best egg quality and quantity. 

A woman is born with all of the eggs she will ever have, and over time they diminish in number and cellular quality. This decline explains why a woman in her 40s has only a five percent chance of becoming pregnant each month; her eggs are also more likely to develop abnormal chromosomes after the age of 45.
Basic fertility testing, including antral follicle counts and hormone and AMH blood testing, assesses a woman’s ovarian reserve. A clearer picture of egg quantity and ovarian function may lead a woman to opt for elective fertility preservation.

How many eggs are needed to be stored to achieve a pregnancy?
Based on preliminary data from our own studies and those of others, egg thaw rates of 75% and fertilisation rates of 75% are anticipated in women up to 38 years of age. Thus, if 10 eggs are frozen, seven are expected to survive the thaw, and five to six are expected to fertilise and become embryos. Usually three to four embryos are transferred in women up to 38 years of age. We recommend that 10 eggs be stored for each pregnancy attempt, and most women of up to 38 years of age can expect to harvest 10 to 20 eggs per cycle.

Is egg freezing safe?
To date, approximately 5,000 babies have been born from frozen eggs. The largest published study – of over 900 such babies – showed no increased rate of birth defects when compared to the general population. Additionally, results from one study showed no increased rates of chromosomal defects between embryos derived from frozen eggs and those derived from fresh eggs. In 2014, a new study showed that pregnancy complications were not increased after egg freezing. There have also been over 300,000 children born worldwide from frozen embryos using primarily slow-freeze cryopreservation techniques, without an increase in birth defects. Although these data are reassuring, it will take many years of further study to ensure that babies born from egg freezing technology have no higher rates of birth defects than those conceived via other means.

How long can the eggs remain frozen?
Based on scientific evidence, as well as clinical experience in achieving pregnancies with frozen embryos – in one case the embryo was frozen for 10 years – we are confident that long-term storage of frozen eggs does not result in any decrease in quality.

How is the process done?
In order to retrieve eggs for freezing, a patient undergoes the same hormone injection process as in vitro fertilization. The only difference is that following egg retrieval, the eggs are frozen for a period before they are thawed, fertilised and transferred to the uterus as embryos.

It takes approximately two to three weeks to complete the egg freezing cycle, which is consistent with the initial stages of the IVF process, including 10 to 14 days of hormone injections to stimulate the ovaries and ripen multiple eggs.

Once the eggs have adequately matured, they are removed with a needle that is carefully placed through the vagina under ultrasound guidance. This procedure is done under intravenous sedation and is not painful. The eggs are then immediately frozen. When the patient is ready to attempt pregnancy, which can be several years later, the eggs are thawed, injected with a single sperm to achieve fertilisation, and then transferred to the uterus as embryos.

What is the cost of egg freezing?
The costs of egg freezing are identical to those of routine IVF. In general, it costs AED 30,000 or USD 8,500 to undergo an egg freezing cycle in the UAE. This estimate includes all testing, monitoring, medications and egg freezing. The egg freezing fee includes the storage fee up to the end of the calendar year. There will be an additional annual storage fee beginning in January of the next full calendar year. The egg thaw, fertilisation and embryo transfer procedure costs roughly USD 5,000, which is payable at the time of egg thaw. 

What tests can tell me how many eggs are there in my body? 
Anti-Mullerian hormone (AMH) testing is a blood test that is used to find out the number of eggs remaining in the body. The test can be undertaken in any phase of the menstrual cycle, regardless of the time, as unlike other hormones AMH levels do not fluctuate during the cycle. It may help to define a woman’s fertility potential and ovarian reserve, and can also tell a woman about her response when injections are given to stimulate the ovaries.