Egg Freezing and Storage

Egg (Oocyte) freezing is a method of fertility preservation for use in a female’s future fertility treatment. Some women wish to freeze their eggs for medical reasons, for example if they are diagnosed with cancer and will require chemotherapy/radiotherapy, at risk of early menopause or other illnesses. Other women wish to freeze their eggs to give them a greater chance of conceiving at an older age. Women may also wish to defer child bearing due to seeking higher levels of education, career prioritisation or not finding a partner. This is termed ‘social egg freezing’.

With regard to egg freezing success rates, the use of frozen-thawed embryos as opposed to frozen-thawed eggs is widely recognised as giving a better chance of having a baby. However, there are a number of circumstances where egg freezing is the best or only option available. 

Although the intention of freezing eggs for social reasons is to maximise the chance of having a baby and egg freezing rates are good, it should not solely be relied upon. Trying naturally should not be delayed, on the strength of having stored eggs, as these frozen eggs may not yield a pregnancy or live birth. Thus, egg freezing should not be thought of as an “insurance policy” as it is not a guarantee of success in the future.

Despite huge advances in egg freezing success rates, some eggs do not survive during the freezing and thawing processes – even with the use of vitrification techniques employed by CRGH – and not every fertilised egg progresses to become a viable embryo. This often means two or three cycles of stimulation, which can make the cost of egg freezing challenging for women to bear. Please visit our Secure egg freezing page for more information on costs.

For information on our egg freezing cycle packages visit our Secure™ page.


How are the eggs frozen?

There are two methods available for egg freezing (cryopreservation): slow freezing and vitrification. Slow freezing can result in dehydration of the egg as it can trap the water content within it making it more susceptible to ice crystal formation, which can cause damage to the egg. This was a frequent problem in the early years of egg freezing. However, vitrification or “ultra-rapid” freezing minimises the formation of ice crystals and thus the risk of damage to the egg is minimised. Vitrification has therefore made egg freezing a viable option for women wishing to preserve their fertility.

CRGH how does egg freezing work infographic

Infographic – How does egg freezing work? © The Centre for Reproductive & Genetic Health


What is the success rate of frozen thawed eggs?

Since the advent of vitrification, the survival of frozen eggs has dramatically increased. We therefore often use frozen eggs in our egg donation programme. The live birth rate per frozen thawed cycle of donated vitrified eggs was 41.1% (115/280) and per embryo transfer 44.1% (115/261) for frozen egg recipient treatment from 2008 to 2020 (all donated eggs were from donors <36 years of age).

At CRGH we have been freezing eggs since 2008. By the end of 2020, we had performed 1462 cycles of own-egg freezing and 101 egg thaw cycles of patients’ own eggs with the aim of embryo transfer in the same cycle.

The following table shows the outcomes for CRGH “Own-Egg Thaw + Embryo Transfer (ET)” cycles across all age categories compared with national figures from the Human Fertilisation Embryology Authority (HFEA). The HFEA figures include both slow-frozen and vitrified eggs.


   All Ages  CRGH Egg Thaw Data 2008-2020 HFEA Data
Own-egg thaw cycles

(average age at time of freeze 36.8)

Egg Survival Rate 71% (666/938) 62.3%2
Live birth Rate / Thaw cycle 30.7% (31/101) 18%1


As with other forms of fertility treatment, the chance of success is dependent on the age of the woman at the time the eggs were frozen. The success rate of egg freezing is considerably lower for women in the older age group. The HFEA’s most up to date report on egg freezing (2018) advises where women over the age of 40 freeze their own eggs, the likelihood of a future pregnancy is very slim and cautions “against this being a sensible option for this group of women”3.  Freezing eggs at a younger age would result in a higher success rate in the future. The following graph shows the CRGH live birth rates according to the woman’s age when the eggs were stored per thaw cycle (PTC).


Live birth rate per ‘thaw cycle + ET’ by the woman’s age when eggs were stored


The HFEA data in the above graph should be interpreted with caution as this data “does not automatically link freeze cycles with thaw treatment cycles”4.

It also quite important to clarify that the age eggs were frozen is not the only factor but the number of eggs thawed is an equally important factor. The table below shows the live birth rate according to the age and number of eggs thawed at the CRGH.


  <10 eggs ≥10 eggs
Age eggs were frozen (years) Live birth rate Number of thaw cycles Live birth rate Number of thaw cycles
<35 42.9% 6/14 63.6% 7/11
35 – 37 50% 6/12 36.4% 4/11
38 – 39 27.3% 3/11 23.1% 3/13
≥40 4.3% 1/23 16.7% 1/6
TOTAL 26.7% 16/60 36.6% 15/41

Please note that the small number of patients thawing their own eggs for embryo creation and embryo transfer can make a large difference to the pregnancy and live birth rate presented in the table above. 


What does the egg freezing process entail?

The egg freezing procedure involves administering injections to stimulate the ovaries for around 12 days. Patients will typically give themselves injections of these drugs for 9-12 days and make visits to the clinic during this period for both blood work and scans to ensure that the drugs are working properly. We will adjust medication levels as required. The treatment takes approximately two weeks.

Following this, the eggs are collected under sedation. This procedure is done in our operating theatre and takes approximately 20-30 minutes. You will require a recovery period in the clinic before going home. Typically, we expect that you will get your period within 3-10 days of the procedure.


What is Abdominal Egg Collection?

CRGH is able to offer transabdominal egg retrieval in addition to the more common transvaginal method.

The abdominal route is used where the patient’s ovaries are difficult to access. It can also be performed where there are cultural or religious factors, which make the transvaginal route inappropriate or undesirable.

Transabdominal egg retrieval is performed under deep sedation. The doctor reaches the ovary using a needle through the abdomen, guided by continuous ultrasound.

Abdominal egg retrieval

Abdominal Egg Retrieval © CRGH

Your CRGH clinician will be pleased to discuss your options as part of your treatment plan.


What are the risks of egg freezing?

Egg freezing is generally safe. However, some women experience some side effects from their fertility drugs. These are usually mild but some women may develop ovarian hyperstimulation syndrome (OHSS). OHSS occurs in women who are sensitive to the fertility medications resulting in too many eggs developing in the ovaries, which can become very large and painful. Around a third of women will have mild OHSS, which can be managed with pain relief. Very few women develop moderate to severe OHSS.

Symptoms of OHSS include:

  • Swollen tummy
  • Nausea and vomiting
  • Shortness of breath or
  • Reduced urine output. 

If you develop any of the above symptoms, please contact CRGH or go to A&E department.

There is a very small risk of pelvic infection after the egg collection. Symptoms include but not limited to:

  • Fever
  • Moderate to severe lower abdominal pain or
  • Malodorous vaginal discharge. 

Please contact CRGH or go to A&E department if you have any of these symptoms.

There is a very small risk of internal bleeding or injury to the surrounding tissue such as bowel. Please contact CRGH or go to your local A&E if you have any of the following:

  • Abdominal pain
  • Shortness of breath
  • Shoulder tip pain
  • Dizzy
  • Abdominal swelling
  • Fever, nausea and vomiting
  • Heavy vaginal bleeding
  • Diarrhoea or
  • Feeling unwell.

There is a very small risk of clot in the leg or lungs. Symptoms of a blood clot include:

  • Throbbing or cramping pain, swelling, redness and warmth in a leg or arm
  • Sudden breathlessness
  • Sharp chest pain (may be worse when you breathe in) and
  • A cough or coughing up blood. 

Please contact CRGH and go to A&E immediately if you have symptoms suggestive of a blood clot.

There is a very small risk of ovarian torsion. This is when an ovary becomes twisted around the tissues that support it. Ovarian torsion can cause symptoms such as but not limited to severe, sudden pain in the lower abdomen, nausea and vomiting. Ovarian torsion is a medical emergency. Please contact CRGH and go to A&E immediately if you have symptoms suggestive of ovarian torsion. Sometimes, you will require surgery (such as laparoscopy) to untwist the ovary and in rare occasions removal of the ovary (oophorectomy).  

If you develop any of the above symptoms or have any concerns, please contact CRGH land line 0207 837 2905 or call our out of hours clinical support line on 07801 079524 and go to your local Accident and Emergency Department .

For further details regarding the risks associated with egg freezing, please discuss with your consultant.



How will the frozen eggs be fertilised?

Freezing and thawing hardens the shell of the egg known as the zona pellucida, which can lead to reduced ability of a sperm to penetrate the outside of the egg by routine IVF, resulting in a very low fertilisation rate.

Therefore, a single sperm is injected mechanically into the egg after thawing it in order to achieve optimum fertilisation rates.

This technique is called intracytoplasmic sperm injection (ICSI).  It is now possible to achieve similar fertilisation rates with fresh and frozen eggs with ICSI.


Does egg freezing treatment decrease the chance of natural conception in the future?

Egg freezing does not decrease the chance of natural conception. Women are born with a finite number of eggs known as “ovarian reserve”. There is a constant decline in the number of eggs per month. In a natural cycle, a cohort of follicles (fluid filled sacs which contain the eggs) are recruited. One of the follicles will become a dominant follicle in response to the natural hormone “follicle stimulating hormone” and the remaining follicles will wither. A new cohort of follicles will be recruited for the subsequent month.

In egg freezing, we are stimulating more of these follicles to grow eggs, which have already been recruited. As more follicles grow, more eggs are collected. The hormones given in egg freezing do not recruit more follicles than what is there and therefore this should have no long-term effect on fertility or result in early menopause.


How long can eggs be stored?

The law allows the storage of your eggs for any period up to 10 years but in cases where you or your partner are prematurely infertile or likely to become prematurely infertile, you may store for longer, up to 55 years.

Causes of premature infertility can include chemotherapy treatment or early menopause. Although you can consent up to a maximum of 55 years, your medical practitioner will need to certify in writing that the medical criteria for premature infertility have been met for storage to continue for more than 10 years. When the criteria have been met, the storage period will be extended by 10 years from the date the criteria are met.

The storage period can then be extended by further 10 year periods (up to a maximum of 55 years) at any time within each extended storage period if it is shown that the criteria continue to be met.


Can I get support during egg freezing?

Family and friends can be a source of emotional support when you embark on egg freezing. However, you may find it helpful to get extra support from one of our counsellors who have experience of the egg freezing process and can relate to exactly what you are going through. Please feel free to contact our counsellors directly.


How much to freeze eggs in the UK?

One of the things we’re often asked is “how much to freeze eggs in the UK”. We know that cost is one of the big factors when people are considering egg freezing. With that in mind, we have created our Secure egg freezing package which aims to minimise costs while achieving the best results.


What are the options available if a person providing gametes or resulting embryos dies or becomes mentally incapacitated?

On the consent forms given to you by the clinic, you will be asked to specify your wishes as to what you consent to with your embryos or eggs in the result of your death or mental incapacitation. You can consent to your eggs/embryos being used for:

  1. Your partner’s treatment*
  2. Training purposes (please note embryos will only be used for training if the other gamete provider has also consented)
  3. Someone else’s treatment. Please note that in this instance you would be becoming an egg/embryo donor and further consent forms will need to be completed and counselling attended. Please contact CRGH for further information.

*If you are a female and storing eggs/embryos and wish to donate your eggs/embryo to your partner, you will also need to complete additional forms so please contact the clinic.


Is it possible to register a deceased partner as a parent of a child resulting from treatment?

In the event of a female patients’ death, she will not be able to be named as the legal parent of a child being born. This is because in the UK the woman giving birth is automatically the legal parent of any child born.

In the event of the male partner’s death, yes, it is possible. Please ensure you have discussed this with your partner so you are aware of each others wishes. There is a section on the MT consent form for the male partner to tick if he wishes to be named as the legal parent in the event of his death prior to a child being born. Please note if donor sperm is being used, your partner can still be named as a legal parent in the event of his death but you must ask the clinic for a PBR consent form.

Please see the following webpage for further information:


Contact us

If you have any further queries about egg freezing please do not hesitate to contact us by phone 020 7837 2905 or email



1. HFEA Fertility treatment 2019 – Trends and figures (underlying dataset)

2. HFEA Fertility treatment 2014 – Trends and figures

3. HFEA Egg freezing in fertility treatment – Trends and figures 2010-2016

4. HFEA Fertility treatment 2014-2016 – Trends and figures


IVF Packages With Access Fertility

IVF Packages With Access Fertility
CRGH is partnering with Access Fertility to offer a series of IVF programmes and packages. For more information please click below.

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