Vitrification for fertility preservation

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.

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What is involved?

Egg collection

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.

Vitrification

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.

Thawing, insemination, incubation

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.

Embryo transfer

All being well, one or two successfully developed embryos will be transferred to your womb a few days later.

Objective statistics and expectations, using vitrification

These simple statistics are based on a single treatment cycle yielding 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 8 of these, on average, will be mature and suitable for freezing.

We would anticipate that all of them would survive the freezing and thawing processes successfully. Upon thawing, the eggs are subjected to ICSI and fertilisation would be confirmed the next day. We can estimate that there would be approximately 6 viable embryos. On average, depending upon the age of the egg at freezing, each of those viable embryos has a 15-30% chance of leading to a live birth. Therefore, the original group of 10 eggs should lead to a 60-80% chance (cumulative) of a live birth.

Of course there will be wide individual variation around each of these figures, but they do indicate the potential success of the treatment. Younger women could expect to produce more than 10 eggs, each of which would have a higher expectation of implantation than those of older women. Hence, the younger the woman at the stage of egg vitrification, the better the results that can be expected. The age of the woman at the stage of thawing and implantation has a negligible impact upon outcome.

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