Egg freezing is the process whereby women opt to freeze their eggs in order to preserve their fertility. The desire to undergo this type of treatment can be for a variety of different reasons including medical and also social reasons.
The process itself involves IVF procedures to stimulate a woman's ovaries to produce a cohort of eggs which are then surgically removed and stored for future use in order to create a pregnancy and live birth, at a time when the patients own fertility may have been compromised.
New techniques for egg freezing now offer the chance for some women to give birth to their own genetic child, even after her fresh eggs have been compromised or she can no longer produce her own eggs and hundreds of babies have been born worldwide following the use of frozen eggs.
Each patient is assessed individually who presents requesting that her eggs are frozen. It is recommended that women over the age of 38 consider very carefully the implications of proceeding with this process since the quality of a woman's eggs significantly declines after this age. Nevertheless each patient will be seen by one of our consultants and all the associated risks of proceeding discussed at the time of consultation.
Detailed below are, broadly speaking, the main types of reasons a woman may wish to cryopreserve her eggs
- She has a life threatening medical condition, the treatment of which could render her ovaries inactive therefore eliminating the chance of the woman being able to produce her own eggs after she has recovered from the condition. These patients are seen immediately and treated as ‘emergency' cases.
- She has a non-life threatening medical condition which may reduce her fertile life span or prevent her from trying to get pregnant whilst treatment is on-going for that particular condition
- There is a history of early menopause in the family
- She is a single woman who is not currently in a relationship, who is conscious of her own declining fertility as she gets older, and who wishes to preserve her ‘younger' eggs for possible use in the future to have her own genetic child.
- She is in a stable relationship, but is not in a position to start a family due to social, economic, or emotional reasons. She would like to preserve her potential of having a family at a later stage in her life when she would be in a position more conducive to bringing up children.
In couples in whom there is personal or religious belief which prevents more than a defined number of eggs to be fertilised (during IVF treatment), the remaining eggs that have not been inseminated could then be frozen for future use.
In the very rare occasions, during a standard IVF treatment cycle and on the day of the egg collection (the procedure whereby eggs are obtained from the woman's ovaries), when the semen sample is not available (for whatever reasons) to complete the process of fertilisation of the eggs, the collected eggs could be cryopreserved as an emergency measure. The frozen eggs could then be used in the future, perhaps in less stressful circumstances, when it can be guaranteed that sperm is available. The rest of the process of fertilisation of eggs and transfer of embryos can then be completed at a later date. Otherwise, without the facility of egg cryopreservation, the eggs would have to be disposed of, thus wasting a precious IVF treatment cycle.
It should however be understood that emergency cryopreservation of eggs should be considered with great care and a great deal of thinking, as egg freezing is a relative new treatment modality and experience with it is limited.
There is certainly no guarantee that eggs will survive the freezing and thawing processes, and that children born following the use of frozen-thawed eggs will be normal.
Egg freezing process
Referrals for “emergency” patients requiring immediate egg freezing are received by the centre from the patient's medical or oncology consultant. Patients are given an appointment for as early as possible with one of our consultants and additional appointments will be created if necessary, to ensure that the patient is seen almost immediately upon receipt of the referral.
At consultation the various options open to the patient will be discussed and this will include the following options:
- doing nothing (since the medication may not affect ovarian function)
- freezing of the patient's eggs
- freezing of the patient's embryos (embryos are eggs fertilised by sperm; this is only applicable if the woman has a partner with whom she would wish to have a child in the future).
- Freezing of part of the ovary that contains eggs; this procedure is currently not
available at a BMI centre and the patient will be referred on.
If required the patient will be given additional time to consider her options and another appointment made once she has reached her decision. Once a decision has been made that the patient wishes to proceed with freezing their eggs, the following protocols will be followed:
- A counselling appointment is offered, although this is also available before the decision.
- The full treatment protocol is explained including success rates of the process, the associated risks, the impact of the woman's age on the quality of her eggs, and the chance of a healthy pregnancy and an explanation of all the consents the woman must provide prior to the start of any treatment.
- A list of preliminary blood tests, including tests for the status of HIV, Hepatitis B and Hepatitis C, will be carried out. The centre can only provide egg freezing treatment in the event that these tests are normal.
- All emergency patients can start treatment within a short period of time in line with the appropriate time in their menstrual cycle.
All patients requiring non-emergency elective egg freezing are required to be referred by their General Practitioner or other associated Clinical Specialist. Upon receipt of a referral the following process is followed:
- Patient is requested to have a blood test to test her ovarian reserve. This is a measure of anti-Mullerian hormone (AMH) which will provide an indication of the woman's fertility potential and also her response to fertility drugs.
- An appointment for a consultation with one of our consultants will be booked for the patient. At consultation the various options open to the patient will be discussed and this will include the following options: 1.doing nothing as the AMH level may indicate her ovarian reserve is unsuitable for egg freezing or 2.freezing the patients eggs
Following consultation the patient is given time to consider their options.
If proceeding with treatment an appointment with the counsellor is offered.
The full treatment protocol is explained including success rates of the process, the associated risks, the impact of the woman's age on the quality of her eggs, and the chance of a healthy pregnancy and an explanation of all the consents the woman must provide prior to the start of any treatment.
A list of preliminary blood tests, including tests for the status of HIV, Hepatitis B and Hepatitis C, will be carried out. The centre can only provide egg freezing treatment in the event that these tests are normal.
Provided the patient meets all the required criteria from the centre they can proceed with treatment at a time to suit them alongside existing clinical activity within the centre.
Egg collection and freezing
The treatment programme for each patient is designed differently depending on the outcome of the preliminary tests and for emergency patients there will be a shorter ‘work-up' time prior to her eggs being collected. The treatment is very similar to IVF treatment, except with egg freezing, the eggs are not inseminated with sperm but frozen immediately. Treatment includes the follow points detailed below:
- Daily injections to prevent ovaries from ovulating at the wrong time of the treatment cycle.
- Gonadotrophin drugs given by daily injections to stimulate the ovaries to produce more than one egg, which is what usually occurs in the natural state.
- Regular ultrasound scans at the centre to monitor the number of follicles that are growing (each follicle may contain an egg) and when these have grown sufficiently the patient will be given a day upon which she will have her eggs surgically removed.
- Egg collection can be performed under general anaesthetic or sedation depending on the patient's preference (administered by a Consultant Anaesthetist).
- Eggs are surgically removed using transvaginal ultrasound guidance.
- Tubes containing the fluid aspirated from each follicle are passed to the embryologists who identifies each egg and collects them in a labelled Petri dish and stores them in an incubator
- Each egg is then assessed for suitability for freezing (immature or post-mature eggs will not be frozen)
All suitable eggs are then prepared for freezing using vitrification methods.
Vitrification is a rapid freezing method whereby the egg is placed into a highly concentrated solution of cryoprotectant and quickly immersed into liquid nitrogen at temperature of -1960C using patient specific labelled plasticware designed for this purpose
The eggs remain in storage until future use or until her consent to store these eggs expires, whichever comes first.
Storage Consent Period
Under current regulations from the Human Fertilisation and Embryology Authority (HFEA), eggs can remain in storage up to a maximum of ten years although in some circumstances this period of time can be extended up to 55 years. It should be understood that once the consented period of storage is reached, the eggs have to be thawed in accordance with current legislation.
Using frozen eggs to conceive
When a woman wishes to use her eggs to try and achieve a pregnancy she will return for a consultation with her consultant. During this consultation the following points will be discussed:
- General medical health and risks of pregnancy
- Chances of success (influenced by total number of eggs available, the number of eggs the patient wishes to thaw at each attempt, the survival rate of frozen eggs following thawing, and the chance that these eggs may be fertilised)
- Assessment of the welfare of any resulting child
- Required consents for the procedure
- An explanation of the frozen egg/embryo replacement procedure
Each patient has an individualised hormone replacement therapy treatment cycle to ensure the uterus is at its most receptive to receive an embryo and maximise the chances of this embryo implanting. This includes:
- Single injection to induce a temporary menopausal state
- Oral hormone tablets (Progynova)
- 2 to 3 transvaginal ultrasound scans
Once the uterine lining has reached a suitable thickness, a day for the egg warming
Eggs are taken out of the liquid nitrogen and the cryoprotectant removed. Each surviving egg is injected with a single sperm (intracytoplasmic sperm injection) from the woman's partner or from a donor. The resultant fertilised embryos are cultured until they have reached the blastocyst and then transferred back into the uterus.
Sometimes embryos will be transferred before they reach the blastocyst stage and this is dependent on the number and quality of the embryos.
A pregnancy test is carried out at a specified time following embryo/blastocyst transfer to establish if the treatment has been successful or not. The success of this treatment is dependent on a variety of different factors and these are discussed at the time of consultation.
Egg freezing is a relatively new fertility preservation technique. Only a relatively small number of babies (perhaps in the thousands) have been born safely after egg freezing and thawing. It should be clearly understood that there is no guarantee that the eggs will survive the freezing and the subsequent thawing processes, nor any guarantee that the eggs will necessarily fertilise. As with all types of fertility treatment, no clinic can guarantee that the procedure will result in a successful pregnancy.
There is also no assurance that babies born following egg freezing and subsequent procedure will always be normal, although research studies so far has been relatively reassuring.
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