Does egg freezing work, should I get tested?
During fetal development, the female baby develops her own store of eggs – approximately 4 million in fact.
By the time the girl has reached puberty, many of these have disappeared – though we don’t know why. At puberty there are about 400,000 eggs in the ovaries, and these will gradually be used up over the next 40 years, until the menopause is reached – on average around the age of 52.
Unlike males, who produce sperm continuously throughout life, women cannot make eggs after birth, and simply use up their egg stock bit by bit. One would think that nearly half a million eggs would be enough to last a couple of centuries at least – unfortunately though, they are 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 going on the pill to suppress ovulation, the menopause will still arrive at its allocated time – pre-ordained at birth by the girl’s 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.
Q: What exactly is egg freezing?
A: 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).
Q: Why would anyone want to freeze their eggs?
A: 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. The 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.
The other main reason is so called “social” egg freezing. 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.
Q: Should I get tested?
A: 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).
Q: Can I freeze my eggs at any age?
A: No. 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! From smaller numbers, good luck may also be needed. At Bath Fertility we have had lucky patients, confirming that egg freezing really does work in practise.