In 2017, more Australian women are having children later in life. In two generations, the average age of a childbearing mother has risen from 25 to 31.
And for some, thanks to the evolution of such technologies as rapid egg freezing, this comes at a point in their life that they may prefer. A potential pregnancy put on hold.
While the reasons for this are many -- illness, career prospects or being without a partner, to name a few -- fertility experts warn that these changes stand in the face of a hard, rigid biological truth.
"Socially, there has been a massive change in the last forty years around women's fertility and their lives. The problem is our biology hasn't changed and women need to understand that," obstetrician-gynaecologist and fertility specialist from IVF Australia Dr Juliette Koch told HuffPost Australia.
By the time women are ready to freeze their eggs, it is not biologically the greatest time to be doing so. That's why this is so complex.
"We are all born with a certain number of eggs with those eggs declining over time in number and quality. Biologically speaking our time for pregnancy is in our 20's. Given that that isn't the case anymore, there lies a big problem and we need to talk about it."
Egg freezing is one part of the picture. Termed 'oocyte cryopreservation', it is process by which a woman's eggs are extracted, frozen and stored to preserve reproductive potential.
The method has evolved into what we now know of as 'social' egg freezing, garnering the attention of global tech companies who, in recent years, have begun offering it to their female employees as part of a string of family planning benefits.
But its beginnings are quite different.
A look back at fertility preservation
Fertility preservation techniques have been cultivated for years, starting out as the only childbearing path for female and and male cancer patients pursuing chemotherapy.
"We've been trying to do this for decades. Sperm freezing has been around for at least fifty years, well before in vitro fertilisation (IVF)," Professor Chris O'Neil, Head Of the Human Reproductive Unit at the Kolling Institute of Medical Research told HuffPost Australia.
"Many forms of chemotherapy will cause loss of the egg reserve from the ovaries, just as it does for sperm from the testes. So advances in this technology, apart from those social reasons, has an important medical need."
When IVF became viable in the 1980s, discussion moved into the potential of frozen embryos.
"The most common group were those women with breast cancer. They'd have their surgery and then there would be a lag between surgery and chemotherapy where you could do a cycle of IVF," Professor Koch added.
"Many of these women with a partner have had children following their chemotherapy by the use of frozen embryos up to five to ten years later, so that was a very successful option."
For single women, the option of slow-freezing eggs became viable in the 1990s with the first successful live birth occurring in 1999.
"It has really only become successful in the last decade. That is, to a large amount, the technological advance of vitrification that has taken it from a clinically non-viable to an increasingly viable option," O'Neill said.
The advent of rapid freezing
When it comes to freezing, the oocyte or egg presents a particularly challenging piece of physics. Here is O'Neill's explanation:
"The egg is a very large cell -- much larger than cells throughout the body -- and it carries a lot of water. When you freeze it with conventional methods, ice crystals are formed that cause damage to the structures within the cell.
"The other side is the egg has its genetic material arranged in a very particular fashion. All of the chromosomes are set up on fibres that are waiting for fertilisation to occur and they are very unstable. The freeze / thaw process can damage that arrangement and lead to genetic abnormalities."
The major advance in the field came with vitrification or rapid freezing.
"Rather than getting conventional ice crystal formation, you get a frozen state which is much more like glass, and poses less risk of damage," O'Neill said.
Social egg freezing is different, and often coined an "insurance policy" against a woman's biological clock.
"As better results came through, it moved towards becoming something that should be potentially available for everyone," Koch said.
"The idea now is women are attempting to insure against their age-related decline in egg quantity and quality.
"The problem is by the time women are ready to freeze their eggs, it is not biologically the greatest time to be doing so. That's why this is so complex."
The process is similar to a cycle of IVF and starts with a period of daily hormone injections, blood tests and monitoring to stimulate egg growth. A 20-minute procedure is then performed in day surgery to extract up to 10 eggs (in one cycle) before the cells from each are removed and studied.
"An egg has to have reached a state of maturity to be frozen," Koch said.
"The mature eggs are put into a solution that protects them from the freezing process before being put into a straw and dunked into liquid nitrogen. They go down to minus 270 degrees."
All you are freezing is potential -- you're banking on an insurance that may never follow through.Juliette Koch
Once vitrified, frozen eggs can be stored for many years without deterioration. But each year, this comes with an added storage cost.
When a woman is ready to use her eggs, a reverse thawing process occurs before they are fertilised with sperm with the aim of developing into an embryo which can be transferred into the woman's uterus.
"For each egg, the chance of having a baby is about four percent," Koch said.
If you have a partner, you may choose to freeze an embryo for future fertility treatment.
This method undergoing an IVF cycle where a woman's ovaries are stimulated with hormone injections prior to the eggs being retrieved and then fertilised with sperm before the resulting embryo is frozen or stored. The frozen embryo is then thawed and transferred back into a woman's uterus.
Embryo freezing has reached a state where you are probably not losing much in the way of viability of an embryo. Chris O'Neill
"One of the features of embryo freezing is those embryos are then being transferred back to the woman in a cycle that has not been subjected to hormonal stimulation. We know very well that the uterus after a natural cycle is a more receptive site for implantation and development," O'Neill said.
"Embryo freezing has reached a state where you are probably not losing much in the way of viability of an embryo."
As a result, success rates after cryopreservation and transfer are not meaningfully different from a normal IVF cycle, according to O'Neill.
Ovarian tissue freezing
For young women with cancer, ovarian stimulation and subsequent egg collection may not be an ideal situation. An emerging area is the cryopreservation of ovarian material over eggs.
"You can take samples of the tissue, freeze and at a later date thaw them. A technology can then be used to mature those in a test tube until they develop into an egg," O'Neill said.
"But this is still in a development phase and is largely experimental at this stage."
Is freezing for me?
Across the globe, egg freezing is becoming increasingly commonplace, with O'Neill pitching the practice as a "rising tide".
"Anecdotally, we know that the best clinics are getting respected rates of fertilisation, with reports showing about a halving in the chance of getting a successful pregnancy," O'Neill said.
But according to Koch, the case in Australia is a little different.
"A lot of the egg banks in Europe and America are trading eggs from women in their early to mid 20's, and a lot of the data comes from these groups. But it isn't relevant to the group of women in Australia who I see who tend to be over 35," Koch said.
What I find women saying to me is, 'I want choice'. They want options. They don't want to regret not doing something. But often they have an unrealistic expectations of what eggs can do.
"Can you compare a 25 year-old from America with a 37-year-old in Australia? It isn't possible.
"What I find women saying to me is, 'I want choice'. They want options. They don't want to regret not doing something. But often they have an unrealistic expectations of what eggs can do."
For Koch, the main risk in pursuing egg freezing is unreliability -- and the possibility of a life put on hold.
"The tricky thing for women who freeze eggs is they are just freezing potential. You're just banking on an insurance that may never follow through."
According to Koch, a lot of women who freeze their eggs may never go onto use them.
"The utilisation rates are very low. I think that is interesting and again it makes you question why people are doing this," Koch said. "By the time women are ready to freeze their eggs, it is not biologically the greatest time to be doing so. That's why this is so complex. But this is a fairly new conversation and we're only starting to talk about it now."
And she calls for an earlier discussions around family planning.
"Some women may consider or go ahead with freezing their eggs, and think that they're sorted. So they start to change their lives because of that decision. What social impact may that have?"
I don't want to discourage women from taking this option if it suits their life plans best. But I think that it is really important that they get the message: at this stage, there are no guarantees.Chris O'Neill
O'Neill shares a similar sentiment.
"For those with medical conditions, there probably aren't many alternatives. It is this or nothing. But for women who are using it for social reasons, it is not in any way a guarantee that you are going to have eggs of quality to make a baby at the end of the process," O'Neill said.
"If the decision is, 'I'm not going to have children now and I'm going to delay it' then maybe it is the right choice. But if the thinking is, 'I can delay it because this is a solution to the problem', then I think that is a high risk strategy.
"I don't want to discourage women from taking this option if it suits their life plans best, but I think that it is really important that they get the message that at this stage, there are no guarantees."
To find out more about female fertility preservation options, book an appointment with a fertility specialist. More information can be found here.
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