There are two reasons why women may choose to freeze their eggs. The first is for health reasons; in particular, for women who wish to preserve their fertility before undergoing cancer treatment. The second is for personal and social reasons as many women may not be ready to have a child during their most fertile years.

You may consider freezing your eggs because you are:

• facing medical treatment that may affect your fertility, such as some forms of cancer treatment
• concerned about your fertility declining as you get older and feel you are not currently in a position to have a child
• at risk of premature menopause or suffer from endometriosis which involves the ovaries.

Step 1. Before you agree to the freezing and storage of your eggs, your doctor will explain the process involved, including the risks and chance of success. Your clinic should also offer you the opportunity to discuss your feelings and any concerns you may have with a specialist counsellor.

Step 2. You will be screened for infectious diseases, including HIV and Hepatitis B and C.

Step 3. You will have a course of fertility drugs (usually daily injections for 8-14 days) and the development of follicles (fluid filled sacs containing eggs) will be monitored with ultrasound examinations and blood tests.

Step 4. When the eggs are mature they will be retrieved in an ultrasound guided procedure under light anaesthetic. This is usually done in a hospital and requires you to be there for about four hours.

Step 5. The eggs are then frozen and stored in liquid nitrogen.

When you are ready to attempt a pregnancy, your eggs are thawed and then fertilised with your partner’s or a donor’s sperm. If healthy embryos develop, one is transferred to the uterus and any remaining embryos can be frozen for later use.

Biologically, eggs can be stored indefinitely. However, in Victoria the legal storage time limit is 10 years, after which time you can apply for an extension. You must let the clinic know if you change address so that they can contact you if the storage time limit is approaching.

The chance of a live birth from frozen ‘vitrified’ eggs  is similar to the chance from ‘fresh’ eggs which are usually used in IVF treatment. The two most important factors that determine the chance of having a baby from frozen eggs are your age when your eggs are frozen and the number of eggs that are stored.

The number and quality of the eggs that develop when the ovaries are stimulated decline with increasing age. A woman in her early thirties might have 15-20 eggs available for freezing after the hormone stimulation, but for women in their late thirties and early forties the number is usually much lower. Also, as women age they are more likely to have eggs with chromosomal abnormalities.

The number of eggs available for freezing and their quality is important because in every step there is a risk that some are lost. Of the eggs that are retrieved, some may not be suitable for freezing, some may not survive the freezing and thawing processes, and some may not fertilise or develop into normal embryos. Of the embryos that are transferred, only some will result in a pregnancy, and some pregnancies miscarry.

The following graph, published in the journal Human Reproduction in 2017, estimates the probability of a live birth according to how many mature eggs a woman freezes at various ages. The graph shows that a woman who freezes 10 eggs at the age of 44 has about an 8 per cent chance of having a baby, whereas a woman who freezes 10 eggs under the age of 35 has about a 70 per cent chance.

The method for freezing eggs varies between clinics but studies show that the most effective method for freezing eggs is a rapid method called ‘vitrification’.

A small proportion of women have an excessive response to the fertility drugs that are used to stimulate the ovaries. In rare cases this causes ovarian hyperstimulation syndrome (OHSS), a potentially serious condition. Bleeding and infection are very rare complications of the egg retrieval procedure.

Egg freezing is still a relatively new technique and the long-term health of babies born as a result is not known. However, it is reassuring that their health at birth appears to be similar to that of other children.

The other risk to consider is that egg freezing does not guarantee you will have a baby. In the UK, the Human Fertilisation and Embryology Authority says only 18 per cent of women who use their own thawed eggs in IVF treatment currently end up having a baby.

The cost of egg freezing varies between clinics. In most cases there is only a Medicare rebate provided for egg freezing for medical reasons, which means that women who choose to freeze their eggs for other reasons may have considerable out-of-pocket expenses.

Clinics usually charge for:

• management of the hormone stimulation of your ovaries (devising a plan for your treatment and prescribing medication)
• the drugs used to stimulate the ovaries
• the egg collection procedure which may include admission to a private hospital and fees for an anaesthetist  
• freezing and storage of the eggs.

Medicare does not cover the storage of frozen eggs, regardless of whether they are stored for medical or other reasons. This may cost hundreds of dollars for each year your eggs are stored. There will also be costs involved when you decide to use the eggs to try to conceive. The process of thawing the eggs, fertilising them with sperm, and growing embryos for transfer into the uterus can cost thousands of dollars in out-of-pocket expenses not covered by Medicare.

A study of fertility clinics in the US found that the information about egg freezing available on their websites was inadequate. It is important that you are well-informed about all aspects of egg freezing before you decide to proceed. Here are some questions you may wish to ask your doctor:

• Does this clinic use the vitrification method to freeze eggs?
• What is the clinic’s success rate for egg freezing?
• How many eggs have been thawed at this clinic and how many live births have resulted from these thawed eggs?
• What is my chance of having a baby from frozen eggs, considering my personal circumstances such as my age and estimated ovarian reserve (a measure of how many eggs you are likely to produce)?
• How many eggs should I store to have a reasonable chance of having a baby? (Remember that you might require more than one stimulated cycle to retrieve enough eggs to give you an acceptable chance of success further down the track)
• What is the approximate total cost, bearing in mind that I may need more than one stimulation and egg retrieval procedure to yield enough eggs?