More and more of my consultations are about egg freezing. The more women I see the more I wonder how effective it is going to be as far as a realistic hope in producing a baby in the future.

The women that tend to come and see me about egg freezing are often in their mid to late thirties (sometimes older) wanting to have a “fertility snap-shot”, an accurate portrayal of their current fertility to be re-opened at a later time. On the face of it this sounds very sensible and pro-active in terms of reproductive autonomy. It is certainly a very exciting prospect to have the peace of mind and security to know that some of your eggs will be safe from the much-discussed decline with age.

As a clinician, egg freezing seems to be a constructive and positive treatment option, as patients are often quite excited at the prospect of taking control over their future fertility.

This hope is based the acceptance of technological advances. Many women will put a great deal of faith and life planning on the belief that this snap shot will offer a reliable security blanket for the future.

What’s the inevitable but?

My main ‘but’ is around the chances of having a baby at this distant and delayed time in the future? It’s so important to really be clear that what you are freezing may not be not much more than a just a slim hope of success… a far cry from the belief that there will be a good prospect of being able to have a baby in the years to come after treatment.

Of course all women undergoing treatment are counselled that the final outcome cannot be guaranteed but what exactly is the probability of actually having a baby when the eggs are finally thawed, fertilised and transferred? I am sure all clinics will have in their paperwork that the outcome is unknown and patients will sign consent forms along these lines.

But in reality we really do not know what happens to the eggs, embryos and pregnancies in the years to come.

What do we know?

We know that the technology works. We are advised by the professional organisations that egg freezing (using vitrification) is no longer in the research stages and can be used for treatment.

We know that babies have been born using frozen eggs, and certainly there are clinics that publish their frozen egg data.

We know that many clinics widely publicise their egg freezing programs without publishing their data.

We know that frozen eggs are sold to patients for use in egg donation cycles, but without a robust reporting mechanism.

What don’t we know?

This is going to be a longer bit. In the UK there is not an externally verified and published data set concerning frozen eggs. In the fertility field we rely heavily on the HFEA for our data to advise patients but unfortunately the number of patients having egg freezing and their outcomes are not publicly available.

This is because numbers are simply not yet available for us to analyse. The numbers are so important in order for appropriate counselling and advice to be given. We can’t answer the common questions of how many eggs does a women need to freeze with each cycle at a certain age and fertility level (AMH and antral follicle count) ? … and what are the thaw, fertilisation, pregnancy, miscarriage and live birth rates?

One of the biggest and most tricky questions is “how many cycles of egg freezing would I recommend?” Such a difficult question to answer! Every woman will produce a different number of eggs, how they will fertilise is unknown and the number of good embryos that they will produce is even more unknown.

I normally start by describing the pregnancy rates of a fresh cycle of treatment based on age and ovarian reserve and work from there. IVF outcomes from a single cycle in women in their late 30s are good but hardly a certainty of success, and we will need to further reduce the estimate by making the assumption that frozen egg pregnancies are less likely.

There is lots of data available on clinic success rates available on the HFEA website. How useful this data is when choosing a clinic is a wider discussion, but there is no data available on egg freezing outcomes. So how do patients know where they should go?

I’ve read and heard lots of doctors say that there is not that much to egg freezing. This may be the case, but successful freezing that produces eggs that will thaw and ultimately produces a pregnancy is going to be a very specialised and skilled task.

From a prospective patients’ point of view you really want to go to a clinic that has a large amount of experience with successful egg freezing (blogs and articles generally refer to clinics in Spain). As I’ve not worked in Spain I’m unable to comment on this. I do think it is completely justified to ask clinics how many patients they have dealt with for egg freezing and how many have returned to use their eggs. Most importantly, how many babies have been born as a result of treatment? I know that this is a relative new treatment option and rates of thawing, fertilisation and pregnancy are very interesting but it’s really the number of babies born per eggs collected that is most important. For instance if its takes 15 or even 20 eggs to produce a baby then a women may think of alternatives if their predicted egg number is much lower than this.

How valid a treatment is it?

Process “validity” is much used term by the HFEA and other quality assurers, and this generally means that a method is proven to be based on existing or accepted observation and practice. But I question whether egg freezing is a “valid treatment” until we really are confident that there is a realistic chance of pregnancy in the future rather than just an optimistic hope.

What do I do?

I do offer egg freezing but I try to counsel women very clearly that although it appears to be an empowering and exciting option, the outcomes are still unknown.

In a nutshell it’s a long shot and you should consider all options.

Want to know more?

Have a look at these pages on the HFEA website http://www.hfea.gov.uk/8597.html. This is an interesting read on the Times magazine website http://time.com/3959487/egg-freezing-need-to-know/