What is egg freezing?
Egg freezing is the method of storing a woman’s unfertilized eggs to allow her to try to conceive at a later date, when natural conception would be unlikely. It may been seen as a way of preserving the possibility of fertility for women who are not in a position to become pregnant straight away, or whose fertility is at risk for medical reasons such as cancer treatment.
Frozen eggs may be stored for many years without significant deterioration. When the woman is ready to use her eggs, they are warmed, and then fertilized with sperm. The aim is for the fertilized egg to develop into an embryo, which can then be transferred to the woman’s uterus in the hopes of inducing pregnancy.
What is involved in the egg freezing process?
To obtain eggs for freezing, a woman will usually be given hormonal stimulation for 10 – 12 days, enabling a number of eggs (usually 6 – 15) to mature. There are a variety of stimulation techniques available and the women can decide which option she prefers during a discussion with her fertility specialist.
The steps involved in the egg freezing process include the following:
The woman is usually given hormone injections in order to stimulate egg production. The hormones are self-administered by the women at home by a daily injection using a pen device which contains a small needle. Patients are taught how to self-administer the medication during their introductory consultation. There are no significant side effects of the treatment, but some women may feel a little bloated afterwards. Women can continue to carry out all their normal activities throughout their treatment period.
After a certain number of eggs are produced the eggs are collected from the ovaries using an ultrasound guided probe that is inserted into the vagina. A needle runs inside the probe and can be gently passed through the vaginal wall into each ovary allowing the doctor to remove the eggs from the ovary. The procedure is usually carried out under a light general anaesthetic or with sedation and the women can go home around 1 -2 hours after the procedure is complete. Patients are advised not to drive after the procedure and to rest for the reminder of the day.
Once the eggs are collected, they are taken to the laboratory where they undergo a freezing procedure called vitrification. This process involves rapidly freezing the eggs using a procedure that extracts fluid from the eggs to prevent the development of any potentially damaging ice crystals from forming. Once the eggs are vitrified, they may be stored for many years.
Egg freezing success rates
Vitrification for egg freezing is a relatively new procedure and it is still too early to be able to give precise figures for the chance of pregnancy after freezing, future thawing and fertilization of eggs. The chance of success is largely determined by the woman’s age at the time of freezing.
Currently the expected success rates for egg freezing would be:
- For a woman aged 35 or under, one stimulated cycle and subsequent egg collection would result in the collection of around 10 – 12 eggs of which 7 – 9 would be suitable for vitrification and storage.
- Approximately 80-90% of the frozen eggs would survive warming or thawing in the future
- Approximately 50-80% of these surviving eggs would fertilize successfully
- Approximately 80-90% of fertilized eggs would develop into embryos
- A single embryo would have a 20-35% change of developing into a successful pregnancy
Success rates are lower for women over 35 and egg freezing in women over the age of 38 is unlikely to lead to a pregnancy.
A rough estimate of the expected success of the procedure can be determined from an initial assessment of the patient. The number and quality of the eggs in the ovaries can be tested with an ultrasound scan and by using a blood test to test for the amount of a hormone called anti-Mullerian hormone (AMH). The AMH test can provide insight into the quantity of eggs remaining, although it does not give information about the quality of the eggs. A high AMH level indicates many eggs are present and a low AMH level indicates a low number of eggs are present.
It is important to note that egg freezing cannot ever be guaranteed to lead to a pregnancy and birth of a healthy baby later on in life. Women who freeze their eggs may not know the outcome for many years and may lose the opportunity to have a baby naturally.
Can you freeze eggs if you have low AMH?
Egg freezing is a reasonable option for younger women with low AMH levels. These patients would be expected to have good egg quality because of their age and may be advised to freeze eggs as early on as possible as they may run out of their store of eggs earlier than usual.
Who might consider egg freezing?
You might consider egg freezing
- if your fertility is at risk due to a serious illness such as cancer;
- or because you are not in a position to have a baby at this specific time in your life and would like the opportunity to start a family at a later age at which natural fertility is less likely.