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Egg freezing to preserve your fertility

Egg freezing is the process whereby women opt to freeze their eggs in order to preserve their fertility.

Egg freezing is a method of preserving a woman’s fertility so that she has the choice to try and achieve a pregnancy and children in later life. The process is becoming more successful but there are no guarantees that a woman will achieve a pregnancy and live birth.

As a woman gets older her fertility declines and her egg quality declines too therefore by collecting and freezing a ladies eggs this ageing process is halted at the time the eggs are collected and frozen.

There are many reasons why a woman may choose to freeze her eggs :–

  • Premature menopause
  • Career / Financial stability / relationship status
  • Not the right time to start a family
  • Illness rendering the lady infertile or reducing ovarian reserve
  • Cancer treatment involving chemotherapy / radiation
  • Gender affirmation
  • The wish not to have any remaining embryos for ethical reasons after an IVF cycle.
  • 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.

Whatever your reasons for wanting to freeze your eggs the Fertility Clinic at The Priory Hospital are here to support and guide you.

The optimal age range is under 35 years of age. However, if you have decided to consider this option at a later age our Consultants will be happy to assess you and advise the best options for you.

You will have some tests before starting the process – typically an anti-mullerian hormone blood test (AMH) This will measure your ovarian reserve and when combined possibly with an ultrasound scan assessment your Consultant will be able to manage your expectations on the possible number of eggs and the likely number of cycles you will need to realistically give you a chance of a pregnancy.3

  • Blood screening tests - This is a prerequisite for all patients having fertility treatment and should be done within 3 months of starting treatment.
  • Your BMI should be less than 35
  • A transvaginal ultrasound scan
  • You will have an information counselling session with a member of the clinic staff who will discuss, in detail, the treatment process, and all the necessary consent forms will need to be completed.

An Embryologist / Fertility Nurse Specialist will discuss the possibility of freezing and consent during your information counselling appointment prior to commencing your treatment. 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.

Consent to storage is initially up to ten years. This can be extended in blocks of up to 10 years to a maximum of 55 years providing you complete new consent forms to extend your consent before your consent expires. These will be sent to you just prior to 12 months before the expiry date of your consent. When considering how long to consent for, please be aware that if you wish to store your eggs for a period less than 10 years, we will contact you to ask if you wish to consent to store for an additional period before the 10 year ‘renewal period’ commences. If you do not extend your consent within the limits of your consent period, your eggs will be removed from storage and be allowed to perish when your consent to storage expires. Consent periods are independent of payments or storage fees charged to continue to store eggs.

Yes, you can change your consent until the point at which the egg(s) have been fertilized and transferred. If your relationship status changes it is important that you contact as soon as possible as you may wish to vary your consent particularly if you have a new partner and wish them to use your eggs in the event of your death. If you decide you would like your eggs removed from storage please contact the clinic and request the relevant paperwork to be sent out for you to complete and return.

The cost of freezing and storage will be charged annually on the anniversary of initial freezing, please consult the current price list for accurate costings. Please update us on any address changes.

You can consent to the posthumous use of your eggs in the event of your death. If you consent to this eggs can legally be stored for up to a maximum of 10 years from the date of death. This period CANNOT be extended.

If you become incapacitated you can consent to the storage and use of a maximum of 10 years, this period CANNOT be extended unless you regain mental capacity in the opinion of a medical practitioner. In both cases if you consent to a period of time shorter than 10 years this will be the maximum time your samples can remain in storage. If your partner is not named on your consent form(s) they cannot legally use your eggs even if you have provided legal consent to posthumous use or use if you become mentally incapacitated.

After your death or if you become mentally incapacitated treatment would involve a surrogate or donation to a female partner within a same sex relationship, then additional consent forms must be completed to allow treatment to take place, you must also be screened in line with requirements for gamete donors. If eggs in storage are used to create embryos after your death or loss of capacity, those embryos can only be stored and used for 10 years from the date of the certification of the egg provider’s death or loss of capacity, not from the date of first storage of the embryos.

A list of preliminary blood tests, including tests for the status of HIV, Hepatitis B and Hepatitis C, will be carried out. It has been experimentally demonstrated that cross-contamination can occur between liquid nitrogen in which frozen eggs are stored and eggs when infectious agents such as viruses are present in the liquid nitrogen. We therefore need to know that you do not have these viruses before your eggs can be placed within a virus negative storage tank. The centre can only provide egg freezing treatment in the event that these tests are normal. 

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:

  1. doing nothing (since the medication may not affect ovarian function)
  2. freezing of the patient's eggs
  3. 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).
  4. Freezing of part of the ovary that contains eggs; this procedure is currently not
    available at a Circle Health Hospital 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.

In a natural menstrual cycle, a lady produces one mature egg each month. Ovarian stimulation leads to potentially the production of multiple eggs (average number produced is 8-14).

The antral follicles (immature egg sacs) are stimulated with daily injections. After 5 days a second injection is introduced to stop the premature release of the eggs. The average number of days stimulation needed are 10 days however your egg collection date can change due to your response to the drugs.

Egg collection is planned when the follicles are 17mm and above as this is a good indicator that the egg inside is mature. The maturity of the egg is an important factor in egg freezing as they cannot be frozen unless they are the correct maturity. See below.

A carefully timed final injection is given when the follicles are mature – this will start the ovulation process and allow for the eggs to be collected.

The stimulation of the ovaries is monitored with ultrasound scans and if necessary blood tests.

Egg collection takes place early in the morning. You are admitted to the hospital and are shown to a bed either on the ward or the daycase unit.

Once you have been consented by your Consultant. You will be taken to the theatre suite in a gown and following a series of checks you will have a small needle introduced into a vein in your hand. A small plastic tube remains, through which the anaesthetic drugs are administered.

During the procedure you will be given pain killers and medicine to minimalize nausea and vomiting. The eggs are collected using a vaginal scan probe and needle which goes through the vaginal wall into the ovary. The fluid drained is checked by the embryologist looking for the egg. Both ovaries have all the follicles drained however there is no guarantee that each follicle will contain an egg and at the end of the procedure you will be checked to ensure there is no bleeding.

You will then be transferred to the recovery ward where you will wake up before being transferred back to the ward / daycase unit where you will be able to have something to eat and drink. Most patients are fit enough to be discharge by late morning.

The embryologist will phone you mid-afternoon to let you know how many of the eggs were suitable to be frozen.

The eggs are vitrified which means they are frozen to a temperature of -194oC. This is a process used to protect tissue from freezing by stopping ice crystals from forming during the freezing process – this assists in egg freezing, which is typically more delicate than embryo freezing.

Your eggs are prepared for egg freezing by removing the surrounding nurse / support cells with an enzyme.  This allows us to assess the maturity the eggs.  Only mature eggs are able to be vitrified (frozen).

Not all of your eggs will be suitable to be frozen by the embryologist. Eggs collected at an egg collection can be at different stages of maturity. Typically during an egg collection we will see the following egg maturity stages:

Metaphase II (MII) – These are the eggs that are suitable to be frozen on the day off egg collection 

Metaphase I (MI) – These are immature eggs that are not suitable to be frozen.

Germinal Vesicles (GV) – These are very immature eggs and are not suitable to be frozen.

The embryologist will feedback to you the number of eggs suitable for freezing and how many of them were immature.


  • During your treatment you may be at risk of developing Ovarian Hyper stimulation syndrome (OHSS) The use of ultrasound scans and blood tests may reduce the incidence of this happening.
  • You may also not respond to the stimulation drugs. It may be possible to increase the drug dosage during treatment but occasionally it is better to stop and restart treatment on a higher dose.
  • There may be no mature eggs to freeze
  • Your eggs may not survive the defrosting process
  • Your eggs may not survive the ICSI injection process
  • There may be failure of fertilisation
  • There may a negative pregnancy test result.
  • Women who become pregnant at an advanced maternal age have higher risks of gestational diabetes

Egg freezing statistics from the Priory hospital

When looking at success rates for frozen eggs numbers tend to be quite low. HFEA reports that in 2016 178 ladies had treatment using frozen eggs – the success rates were 18% - 39 babies were born but clearly techniques have improved since this last published data.1,4

HFEA studies state that it is not the age of the woman at thaw but the age of the woman at freeze that dictates success rates.1,2

It is suggested that freezing approximately 20 eggs gives the best chance of having a good number of thawed eggs to perform ICSI and increase the chance of pregnancy. Ladies over the age of 35 with reduced ovarian reserve may not achieve this even with more than one attempt at stimulation and egg collection. Many eggs will not survive the defrosting process. The surviving eggs will then need to be injected with sperm ICSI (intracytoplasmic sperm injection) and may not survive this process. Your centre will counsel you about the risks of this.

See Costed Treatment Plan for specific details.

As with all fertility treatment, counselling is offered to those who would like it.  It is in place for the benefit of patients, who may feel stretched emotionally as well as physically. Our counsellor is happy to see you and help you explore anything that worries you.  She will listen in a non-judgemental setting and give you time to explore what you are feeling at this time.

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 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
is arranged.

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 embryo(s) are cultured until they have reached the blastocyst and then one or two embryos are transferred back into the uterus.

Sometimes embryo(s) will be transferred before they reach the blastocyst stage and this is dependent on the number and quality of the embryo(s).

A pregnancy test is carried out at a specified time following embryo 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.

If in the future you do not wish to keep your eggs for your own treatment, you have the option to donate them for use in someone else’s treatment, training or research. If you give consent for storage for use in training after completing your own treatment then it is possible that eggs may be used in training even after your death or mental incapacity as we are unlikely to know that you have died or lost mental capacity, particularly if you are no longer having treatment and would not be in contact with the centre. If you do not wish for this to happen, you should not give consent to storage for use in training. Further information about each of these options will be provided when appropriate.

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. Your chances of success decrease sharply if you are over 35 at the time the eggs were collected.

The HFEA also provide information for patients on their website:

  2.  Alteri A, Pisaturo V, Nogueira D, D’Angelo A. Elective egg freezing without medical indications. Acta Obstetricia et Gynecologica Scandinavica. 2019 Mar 5;98:647–52.
  3. Drost L, E. Shirin Dason, Han J, Doshi T, Scheer A, Greenblatt EM, et al. Patients’ and providers’ perspectives on non-urgent egg freezing decision-making: a thematic analysis. 2023 Feb 8;23.
  4. Edgar DH, Gook DA. A critical appraisal of cryopreservation (slow cooling versus vitrification) of human oocytes and embryos. Human Reproduction Update. 2012 Apr 25;18:536–54.

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