Fertility Preservation

Age has a profound effect on fertility. This is true both for the man and the woman, but it is especially so for the woman. A man continues to make sperm (albeit in diminishing amounts and quality) all his life. A woman is born with every egg she will ever have in her lifetime. Ironically, roughly one third of those eggs have been lost before she is even born, and a further large proportion of those remaining eggs will naturally die before she even reaches puberty. At birth, she will have approximately 2 million eggs. By the time she reaches puberty, her egg number has fallen to only 300,000. From that time on, she will gradually begin to lose the remaining eggs until she reaches the menopause. This is the time when virtually all of her eggs have been depleted. It is a strange biological irony that each hour, a man of reproductive age may make up to 150,000 new sperm while a woman of similar age may lose 2 or 3 of her eggs. This egg loss occurs as a result of natural cell death, which we call apoptosis. It is not just a result of egg loss through the process of ovulation.

A woman’s natural chance of conception is profoundly affected by her age, but there is certainly much biological variability. Each woman is born with a different number of eggs in her ovaries. Each woman will lose her eggs at different rates throughout her reproductive life. Some women at 40 years of age will still have more healthy eggs than other women at 35. It is the biological age of your ovaries, not your years since birth, which will determine how much your fertility age will be affected by your age. It is process over which we have very little control.

How does a woman naturally preserve her fertility? To a very considerable degree, the answer to that question is that she cannot. There are a number of important measures which any woman can carry out, however, to try and ensure that she tries to maintain her fertility for as long as possible. Maintaining good general health is clearly important. There is good evidence that heavy smoking may have a significant impact on ovary function. There is now also good evidence to show that obesity has a significant fertility effect as well, even if the woman is having normal and regular ovulation cycles. Any woman who is having fertility problems, or is wishing to preserve her fertility for the future, should make every effort to ensure that she maintains a normal weight and does not smoke.

It is clearly vitally important for any woman who has a gynaecological disorder, which might potentially affect her fertility, to ensure that these disorders are treated and controlled as best as possible. Any woman with ovarian endometriosis, for example, should make every effort to ensure that her condition is either completely resolved or kept under control. Any young woman taking long-term medications which might affect her reserve of eggs should carefully consider the situation.

But what about the woman who is in excellent health? She has no current or previous gynaecological conditions, she is not obese, and she has never smoked, and she takes no medications. She is 36 years old and has no plans to have a child in the immediate future. At the same time, she certainly does not want to rule out the possibility of being unable to have a child in the future. She is well aware that, as she approaches 37 years of age, her fertility will be half of what it was when she was 20. By the age of 41, it will have halved again. How can she preserve her fertility for the future? Men have been potentially able to do this for a number of decades now. It is a relatively simple process for a man to produce and store a sperm sample, comfortable in the knowledge that this would potentially retain his fertility for an indefinite time into the future. What about the situation for women?

There are a number of good reasons why it has been much easier for a man to preserve his fertility than it has been for a woman:

• A sperm sample is very easy to produce!
• Each sperm sample contains many millions of sperm.
• Sperm cope remarkably well with the freezing and thawing process.

For these very same reasons, it has been much more difficult for a woman to try and preserve her fertility:

• Collecting eggs from a woman is a much more complex process. It involves a surgical procedure which has some risks and dangers.
• An egg retrieval procedure will collect only a small number of eggs on each occasion.
• The human egg has, in the past, coped very poorly with freezing and thawing.

Recent new scientific developments have dramatically changed the situation, however. New techniques for egg freezing and thawing have improved remarkably. For the first time, we are now in a position to offer egg freezing to women who might wish to consider preserving the fertility. Clearly, the ideal solution for our 36-year-old hypothetical woman would be to choose to have a baby before she becomes very much older. If this is not possible, however, storage of eggs may be an increasingly realistic proposition for her. “Social” egg freezing is likely to become more common in the future and is certainly likely to become one of the contentious issues in modern reproductive technology in the years to come.

“Medical” egg freezing has been used for some time for women who find themselves in the appalling dilemma of requiring treatment for a cancer, or other medical condition, which may possibly leave them infertile. Despite being able to collect their eggs efficiently, until recent times we have had to tell these women that successful pregnancies following egg freezing were very infrequent. Results are now improving markedly. New techniques now offer these women the prospect of retaining their fertility for the future once they have completed their cancer therapy.

An alternative form of treatment for some women is to take a small amount of ovary tissue, rather than eggs, and to freeze and store this tissue in the hope that it can be grafted back into the woman's body again after she completes a cancer therapy. This technique should still be regarded as experimental at the present time but it offers great hope for the future.

Can we make new eggs?

At the present time the answer to that question is no. There is the exciting thought, however, that one day new eggs may be able to be generated from stem cells or other similar technologies.