Approximately 400,000 eggs are in the ovaries at puberty. These eggs will gradually be used up over the next 40 years until menopause is reached. On average a woman will reach the menopause at the age of 52.
Unlike males, who produce sperm continuously throughout life, women cannot make eggs after birth. The egg stock is simply used up in batches, not one at a time, and for some women this seemingly wasteful use of their eggs can leave them short, just when they need them.
One day we may understand why so many eggs are just wasted, but at the moment we do not know the reason. Unfortunately, the programmed wastage cannot be stopped, even with use of the pill to suppress ovulation. The menopause will still arrive at its allocated time which is pre-ordained at birth by your genes. At present the only mechanism that seems to prolong fertility slightly is pregnancy itself, which is why some older women with children seem able to become pregnant at an age when another woman trying to conceive for the first time finds it impossible.
We hope one day to understand how suppression of ovulation by natural pregnancy may spare fertility in a way that drugs can’t, but for the moment we have to look to artificial means in the form of egg freezing.
What is egg freezing?
Currently the term is applied to eggs produced by an IVF process. This involves a course of injections of fertility hormones, usually for 10 to 14 days. One or two ultrasound scans are needed to monitor growth of the follicles containing the eggs, which are then collected under sedation using ultrasound guidance.
Instead of being fertilised with sperm, the eggs are frozen using a technique called Vitrification. Once vitrified, the eggs theoretically can be stored indefinitely, although there are regulations regarding storage periods (usually a maximum of 10 years).
Vitrification is one of the most advanced techniques used and results in excellent survival rates of both eggs and embryos, and high pregnancy rates with frozen embryos.
Who might benefit from egg freezing?
The most common reasons for a woman to have their eggs frozen are:
- about to undergo chemotherapy or radiotherapy
- at risk of an early menopause
- couples undergoing IVF treatment who have ethical or religious concerns over embryo freezing
- have not yet met the right partner but may wish to start a family in the future
- undergoing IVF treatment where there is a problem obtaining a sperm sample.
Egg freezing (or oocyte cryopreservation as it is technically known) was initially developed to preserve the fertility of women about to undergo treatment for cancer, which in many cases will kill the eggs as well as the cancer cells leaving them infertile.
Egg freezing technology has developed rapidly in recent years and it has become fairly reliable as a form of treatment, which has led to an extension of its use for other reasons.
Increasingly, modern lifestyles have led to deferment of childbearing such that having a family is preferred at a more mature age. Whilst this can have undoubted benefits, the ovaries remain unaware of the changed priority and continue to carve their way through the reserve egg stock, so the eggs may not be there when they’re really wanted.
Egg freezing means that some eggs can be reserved and protected from the passage of time. The other main reason for egg freezing is when early menopause might be expected because:
- it’s a family trait, or
- a woman has had ovarian tissue removed for disease.
More recently a third group has started to emerge – these women who have requested testing, and found to be heading for an early menopause, often unexpectedly.
What is involved in egg freezing?
If you chose to have your eggs frozen it will involve the same type of treatment as women having IVF. Drugs are used to stimulate your ovaries to produce multiple eggs. 10-14 days after commencing treatment the eggs are collected using an ultrasound guided needle under sedation. This procedure typically takes 10-15 minutes.
Eggs which are mature (i.e. ready to be fertilised) can be frozen using a process called vitrification. Eggs can normally be stored for up to 10 years.
When required for treatment your eggs are thawed and then fertilised using intra-cytoplasmic sperm injection (ICSI), a technique that involves injecting a single sperm into each egg. Resultant embryos are transferred to your uterus at a maximum of two at a time.
How successful is egg freezing?
It is important for women to be realistic about their chances of conceiving using frozen eggs. Survival rates for eggs following freezing depend on the quality of the eggs before freezing, but on average about 70% of frozen eggs will survive the freeze-thaw process. Of the surviving eggs undergoing ICSI we hope about 60% will fertilise.
The use of frozen eggs is still a relatively new technique and as such it is difficult to provide any meaningful statistics regarding pregnancy rates. Success rates worldwide appear to be about 10% per attempt (rates quoted by individual clinics vary from 5% to up to 30%).
In practise we have had many patients who have benefited from egg freezing.
Should I get tested?
You should definitely get tested if early menopause is known in your family. In some families it comes earlier with subsequent generations, so early testing is advised if you want the chance to have children. Anyone having ovarian surgery should also consider testing, if they are yet to have children. The test measures AMH (anti-mullerian hormone) and can be taken at any time in your menstrual cycle. It is an easy check to have for anyone who has a concern or feels time might be running out for any reason. It may be possible to obtain this blood test from your GP. There may well be a charge for it (typically £60-80).
Can I freeze my eggs at any age?
Unfortunately, the usefulness of egg freezing diminishes with age. It is best undertaken before the age of 38, and preferably 36 or younger. There are two reasons for this; quality and quantity. Older eggs are less likely to produce a successful embryo, and also they are less likely to freeze well. Older women generally produce fewer eggs per cycle of stimulations, and not all eggs collected will be suitable for freezing.
To stand a realistic chance of having a baby from frozen eggs, quite a few need to be stored. Some studies suggest as many as forty should be frozen.
Free counselling is available if you are considering egg freezing. This gives you the opportunity to talk to an independent person about your concerns regarding storage of your eggs and their future use.