Egg Freezing: What are the success rates?
The data
Interesting data has been released by the Human Fertilisation and Embryology Authority (HFEA) showing the success rates using frozen oocytes in fertility treatment. The data presented was from 2016 where 1,204 frozen eggs were thawed: of these, 590 eggs were fertilised. Of the 590 eggs fertilised 179 were transferred back to a patient, and out of the embryos transferred, 22 resulted in a pregnancy.
Before people start to fear that egg freezing always yields such low results, it's really important to note that of these patients, 68% were over the age of 35 and several were in their mid 40's at time of freezing their eggs.
Your chances of becoming pregnant heavily depend on your age at the time eggs are frozen, as well and your general health and so is an extremely important determinant on the success rate, in combination with the number of eggs retrieved.
The HFEA also points out that very small numbers of women in the UK who freeze their eggs actually go back to use them, so it's difficult to draw too firm a conclusion from such a small sample.
This data is from 2015. We need to be looking at 2020 data which is more current and in line with the most recent practices and techniques of the Vitrification method of freezing. This method is the fastest way to freeze oocytes, reducing the chance of any damage due to crystal formation and improving the survival on thawing.
What happens during an egg freezing cycle?
A woman is given hormonal stimulation via injection to encourage a high number of eggs to develop in the ovaries
These eggs are then retrieved through the vagina during a procedure that requires light sedation
The eggs are then frozen and stored in liquid nitrogen at -196 C for a maximum of ten years (as per HFEA)
An IVF cycle involving frozen eggs goes something like this:
Eggs which were previously frozen and stored are thawed
The ones that survive the thawing will be fertilised with sperm
Eggs that are successfully fertilised start to develop into embryos
Of the embryos that survive, usually one or two (up to a maximum of three for women over 40) will be transferred to the womb
During the above process, some eggs are expected to be lost - ‘attrition’. There are risks that these eggs may be damaged during the freezing process, they may not survive the thawing, they may not fertilise to make an embryo and the ones that do, may not go on to achieve a pregnancy. From thawing, to fertilisation, to development into an embryo, to transferring the embryo into a womb, eggs are lost at each stage, and there is never any intention that every egg in a treatment cycle will be used. Despite this, the current practices using fast freezing methods (Vitrification) have replaced the slow freezing methods which yield far better results for egg freezing and their survival.
My advice is to become well informed on your choices. Do you start a family earlier with less likelihood of requiring assistance in the future or do you freeze your eggs now as an insurance policy for the future (which you may never end up using). Women are unfortunately stuck between a rock and a hard place as if they do wish to freeze their eggs at an earlier age, for example at 24, they have until 34 to use these eggs. What if women are not ready at the age of 34? We know that the best time to freeze your eggs is between the age of 24 - 30 - age does matter - egg quality declines with age. These issues need to be addressed and these questions answered in order for women to be able to make these important decisions and feel supported from the HFEA and other governing bodies when it comes to safeguarding their fertility and their future family plans.
Right now, petitions are underway in the UK to increase the storage period for frozen eggs from 10 years to something less arbitrary, allowing women to freeze at the earliest and store their eggs until they wish to start their families. Fingers crossed.