The human egg is a very large cell. Until recently we didn’t have technology advanced enough to freeze (and thaw) eggs safely. Ice crystals tended to form, causing damage to the cell. However with vitrification, the technology has improved. We can now vitrify eggs without losing their viability, so that they can then be stored and used later. Here at GCRM, we offer fertility preservation: women go through the IVF stimulation and egg collection processes, but instead of being mixed with sperm the unfertilised eggs are frozen.
Fertility preservation is advised for women who are looking to have a child but perhaps aren’t quite ready yet. It is also advised for pre-transitioning female to male transgender patients.
The technology is relatively new but the results are encouraging, such that units around the world are achieving 25% pregnancy rates using frozen (vitrified) mature eggs. This compares favourably with the success rates for IVF cycles, in patients of the same age. The number of babies born following these procedures is increasing all the time.
Declining fertility is due to the age of the eggs, and therefore fertility preservation is most effective if a woman is young when her eggs are frozen. Nevertheless, it could have a place for women in their mid-30s or older who do not want to have a family just yet. If you feel that fertility preservation might be for you, you can learn more about what is involved below, or download a factsheet.
Putting your fertility on ice is very similar to the start of a standard IVF cycle. It involves a course of daily fertility drug injections for approximately 2 weeks followed by a procedure to remove the eggs.
The eggs are then carefully vitrified and put into store in liquid nitrogen at -196°C. They can be kept under these conditions without deteriorating for an indeterminate length of time.
When you decide that it is time to use these eggs, they will be thawed at the appropriate time of your menstrual cycle and inseminated with a single sperm using intracytoplasmic sperm injection (ICSI). The cells are then placed in an incubator so that fertilisation can take place.
All being well, one or two successfully developed embryos will be transferred to your womb a few days later.
These simple statistics are based on a single treatment cycle producing enough eggs to provide a reasonable chance of success. If you respond well to stimulation treatment so that we collect 10 eggs, we would expect that on average 8 of these will be mature and suitable for freezing.
We would expect all of them would survive the freezing and thawing processes successfully. When thawed, the eggs are injected with an individual sperm (ICSI). On average 6 of these might fertilise and go on and divide. Depending upon the age of the egg at freezing, each of those viable embryos then has a 15-30% chance of leading to a live birth.
Of course, there will be wide variation around these figures, but they do show that treatment can be successful. Younger women could expect to produce more than 10 eggs, each of which would have a higher chance of success than those produced by older women. Hence, the younger you are at the time of egg freezing, the better the results. Your age at the time of thawing and replacing embryos has very little impact on the outcome.