Egg (Oocyte) freezing is a method of storing a woman’s unfertilised eggs to allow her to try to conceive at a later date, when natural conception may be less likely. It may offer the option 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 needing cancer treatment.
Frozen eggs may be stored for many years without significant deterioration. When the woman is ready to use her eggs, they are thawed and then fertilised with sperm by injection of the sperm into the egg (ICSI). The fertilised egg is then cared for in the laboratory to develop into an embryo, which can then be transferred to the woman’s uterus with the aim of becoming pregnant.
The egg freezing process
During every cycle, eggs grow in fluid filled sacs (called follicles) on the ovaries. Normally only 1 egg will mature and be released (through ovulation), whereas the rest will die. Injections are given during the IVF cycle which leads to egg freezing and these injections help all the eggs to mature.
Hormone stimulation of your ovaries
To obtain eggs for freezing, a woman will usually have hormonal stimulation for 10 – 12 days, enabling a number of eggs (usually 6 – 15) to mature. There are a variety of stimulation techniques, and you will decide which is best for you in discussion with your specialist.
The stimulation medications are usually self-administered by a daily injection using a pen device with a small needle. Patients are taught how to do this in an instructive introductory consultation. The injections make the woman feel a little bloated but there are no frequent significant side effects and she can carry out all normal activities throughout the period of stimulation. During the stimulation period, you’ll be monitored via blood tests and ultrasounds.
Choosing to freeze your eggs doesn’t mean you’re robbing yourself of viable eggs from your egg supply (ovarian reserve). The stimulation used mimics your body’s natural processes and the eggs that are stimulated to grow would have grown or died during your natural cycle. This process doesn’t affect future egg supply or lead to premature menopause. Some women who freeze their eggs don’t use them because they later fall pregnant naturally.
When your eggs are ready to be collected, you’ll visit the hospital for a short procedure. You’ll be asleep, so you won’t feel a thing. The procedure itself takes around 15-30 minutes and you can usually go home in 1-2 hours and are advised not to drive and to rest for the reminder of the day.
The eggs are collected from your ovaries using an ultrasound guided probe inserted into the vagina, so there are no cuts or scars. A needle runs inside the probe and can be gently passed through the vaginal wall into each ovary in turn, allowing the doctor to aspirate eggs from the ovary.
Once in the laboratory, the eggs are assessed by the scientist following removal of the outer layer of cells that surround the egg when it is collected from the ovary. The scientist will identify the eggs suitable for freezing. Only mature (Metaphase II stage) eggs are frozen as immature eggs don’t create a viable pregnancy.
Eggs are frozen using a procedure called vitrification. This involves rapid freezing of the eggs using a process called vitrification that avoids potentially damaging ice crystal formation. The eggs (usually two to three at a time) are held on a specially-designed device usually called a straw, labelled with your name and date of birth. Once vitrified, eggs may be stored for many years in liquid nitrogen.
Using your frozen eggs
When you’re ready to use your frozen eggs to try and have a baby, see your specialist to develop a treatment plan.
When it’s time, your eggs will be thawed by removing them from the freezing solution and quickly warming them in special solutions. After a short recovery, the eggs are ready for insemination, usually by injecting a single sperm into the egg (ICSI). After fertilisation, the egg becomes an embryo, and an embryo transfer is performed if the lining of the uterus is optimal for success.
Egg freezing success rates
Vitrification for egg freezing is a relatively new procedure and it is too early to be able to give precise figures for the chance of pregnancy after freezing, future thawing and fertilisation. The chance of success is largely determined by the woman’s age at the time of freezing.
Currently we would expect the success rates for egg freezing would be:
- For a woman aged 35 or under, one stimulated cycle would result in the collection of 10 – 12 eggs of which 7 – 9 would be suitable for vitrification and storage.
- Approximately 70-90% of the eggs would survive warming in the future.
- Approximately 50-80% of surviving eggs would fertilise.
- Approximately 50-90% of fertilised eggs would develop into embryos.
- A single embryo would have a 20-35% change of developing into a pregnancy.
Success rates are lower for women over 35 and are likely to decrease with increasing age:
Live birth predictions by age and number of mature eggs collected. Each curve shows the percent likelihood that a patient of a given age will have at least one live birth1.
The expected success of the procedure can be ascertained from an initial assessment of the ovarian reserve using a blood test for Anti-Mullerian Hormone (AMH) and an ultrasound scan of the ovaries and uterus. The AMH test can provide insight into the quantity of eggs remaining, although it does not give information about the quality of the eggs.
Egg freezing cannot ever be guaranteed to lead to a pregnancy and birth of a healthy baby later 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.
Who might consider egg freezing?
You might consider egg freezing:
- If your fertility is at risk from a serious illness such as cancer;
- If you are not in a position to have a baby right now and would like the opportunity to start a family beyond the age at which fertility naturally declines.
If you are contemplating egg freezing you should also consider other options which may be available to you, such as embryo freezing, donor insemination (for more immediate rather than delayed pregnancy) or the possible use of donor eggs if your own ovarian function is likely to be lost.
How much does it cost to freeze eggs?
In Australia, Medicare provides a rebate for fertility treatments if there is a medical need for the treatment. If you’re choosing to freeze your eggs for non-medical reasons, you won’t receive Medicare assistance and access to medications which stimulate the ovaries. Private insurance does not pay for hospitalisation when Medicare assistance is not provided.
Contact Care Fertility for an individualised quote for the costs associated with egg freezing.