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’.
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, 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.
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.
Infographic – How does egg freezing work? © The Centre for Reproductive & Genetic Health
What is the success rate of frozen thawed eggs?
At the CRGH we have been freezing eggs since 2008. By the end of 2019, we had performed 1184 cycles of own-egg freezing and 95 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 2008-2019||HFEA Data|
|Own-egg thaw cycles||
95 (average age at time of freeze 37.1)
|Egg Survival Rate||72.9% (644/883)||65%2|
|Live birth Rate / Thaw cycle||31.6% (30/95)||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 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”1. 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”3.
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 – 37||50%||6/12||40%||4/10|
|38 – 39||30%||3/10||27.3%||3/11|
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.
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
- 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:
- 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
- Abdominal swelling
- Fever, nausea and vomiting
- Heavy vaginal bleeding
- 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
- A cough or coughing up blood.
Please contact CRGH and go to A&E immediately if you have symptoms suggestive of a blood clot.
For further detail regarding the risks associated with egg freezing, please discuss with your consultant.
If you develop any of the above symptoms or have any concerns, please contact CRGH land line 0207 837 2905 or On call out of hours emergency mobile 07801 079524.
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.
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.
2Calculated from HFEA 2016-03-23-fertility trends 2014 datasheet for years 2010-2014
3HFEA Fertility Treatment 2014-16 Trends and Figures Report