The technology that allows for freezing of eggs rather than embryos has only been with us for a relatively short time, since 1986. During that brief period, egg freezing has increased dramatically, by around 460% in the six years from 2010 to 2016. Why is this? One simple answer is that in a world where societal, work and relationship norms are constantly evolving, one thing that never changes is the relentless ticking of the female body clock.
Egg freezing is one way of dealing with the extraordinary pressures that this creates for women trying to balance social considerations with their equally imperative desire to become mothers one day. The big question is, when? At what age can you freeze eggs with a reasonable chance of a successful outcome? Is freezing eggs at 40 possible and, if so, is it a good idea?
How does egg freezing work?
Egg freezing is a procedure in which a woman’s eggs are stored for future use in fertility treatment. It can be carried out for medical or elective reasons. In a sense, egg freezing became possible as a by-product of the well-known IVF procedure in which a woman’s ovaries are stimulated to produce multiple oocytes which are then fertilized in the laboratory, with the best of the resulting embryos being returned to the maternal uterus. Egg freezing interrupts the IVF process in that after collection, the eggs are frozen and stored for future use. When the time comes, the eggs are thawed and fertilized and the IVF process continues in the normal way.
In the early days of the technique, freezing was carried out through the ‘slow cooling’ method. Although there was some success, the survival rate was low because of the propensity of ice crystals to form, damaging the delicate structure of the eggs. The newer method, now widely used, is known as vitrification, or the cryopreservation of oocytes. This method is significantly more effective and it is the one used in our IVI clinics, where the vitrification of oocytes has developed to the extent that there is a survival rate of around 97% and we obtain the same clinical results as with the use of fresh oocytes.
For a full picture of how this works, you can have a look at the video about the vitrification of oocytes on our IVI YouTube channel.
At what age can you freeze eggs?
The age at which you freeze your eggs is the absolute crux of the matter. It is well known that a woman’s natural fertility starts to decline around the age of 30 and decreases more sharply around the age of 35. This is due to not only a depletion of the ovarian reserve, but also a decline in the quality of the eggs that remain. Put bluntly, older eggs are more likely to have chromosomal abnormalities, This is why women who become pregnant in their early forties have a 40% chance of miscarriage, compared with under 15% for someone in her early twenties.
The biological clock ticks in the ovaries, not the uterus
It is a point worth noting here that a woman’s ‘body clock’ applies specifically to her ovaries and not to her womb. Since eggs frozen at a particular age retain the qualities they had at the time of collection, effectively this means that egg freezing allows for the use of ‘young’ eggs in an older uterus, even if you decide to fertilize and implant these at the age of 40 or 45.
Age at freeze is what matters, not age at thaw
Research has confirmed that the rate of successful outcome decreases as a direct corollary to the increased age of the woman at egg collection, with the highest rates being for eggs collected under the age of 35. The age at thaw, by contrast, shows no such correlation, with success rates being relatively stable over all age ranges. Your overall chance of becoming pregnant with the use of your own frozen eggs is between 60% and 30%, depending on your age at the time of freezing. And so, even though technically you can freeze eggs at any age as long as there are some available, many experts consider that there would be little point in freezing eggs at 40 or later since the chances of miscarriage or foetal anomalies increases and the pregnancy rate is very low in these circumstances.
What about other time constraints?
The natural decline in a woman’s fertility is not the only time constraint surrounding the freezing of eggs. The legal framework in different countries varies on how long the storage of eggs is allowed. This creates a new kind of ‘biological clock’. For example if the storage limit is 10 years, a woman in her mid to late twenties is effectively discouraged from freezing her eggs in spite of being at an ideal age since, with a 10-year limit, the time may well be up before she is ready to thaw and make use of the eggs.
Currently in Sweden, oocytes may only be stored for five years. In the UK the legal limit on egg storage for social reasons is 10 years. , but there may be a limit on the age to undergo the fertility treatment.
Finding out more about egg freezing
In spite of these different regulatory climates, the message is consistent and clear. The younger a woman is when she freezes her eggs, the better the outcome. Before 35 is best, 38 at the latest, and freezing eggs at 40 currently has a very low success rate.
If you would like to find out more, contact any one of our Just use our online contact form or give us a call on +34 960 451 185.