Egg Freezing (Vitrification)
Who may benefit from egg freezing?
There are two main categories of patients who choose to freeze their egg.
- young single women or women who have decided to defer childbearing. Many women are delaying marriage or going on to develop their careers and as a result, delaying having a family. The likelihood of a woman conceiving in her late 30's or early 40's is dramatically lower than in her late 20's and early 30's. The incidence of both subtle and obvious chromosomal abnormalities, also rises very significantly for women in their late 30's and 40's.
- women who have to undergo cancer treatment. If time permits women diagnosed with cancer may undergo an IVF cycle to preserve eggs for future use.
How will the oocytes be collected?
A woman embarking on freezing her eggs would need to go through a conventional cycle of IVF cycle with ovarian stimulation. This invovles the steps outlined in the IVF information page up until the point of fertilisation, where the eggs are frozen instead of being fertilised.
How will the eggs be frozen and stored?
The eggs will be frozen by a method called vitrification. This is a form of ultra-rapid cooling – so quick in fact that no ice crystals are formed during the process. Ice crystals that formed during the “old” freezing technique, have the potential to damage the eggs during the freezing and subsequent thawing technique.
With Vitrification clinics overseas are reporting pregnancy rates that are far superior compared to the “old” freezing technique. This is why IVF Sunshine Coast and IVF Caboolture has adopted Vitrification as the preferred method of freezing.
Once frozen the straws containing the eggs are stored in liquid nitrogen at -196 C. At this time it is believed that frozen eggs can be kept stored for many years, in a similar manner to frozen embryos or sperm.
How can the oocytes be used?
When the frozen eggs are required they would be warmed and placed into standard IVF culture media. Using the currently available freezing and thawing procedures, between 70 and 80% of frozen eggs are expected to survive the freeze/thaw process.
Research has shown that the injection of a single sperm into a previously frozen egg is necessary to obtain fertilisation. This procedure is known as ICSI (Intra-Cytoplasmic Sperm Injection). Using currently available freezing and thawing procedures, around 60% of frozen oocytes injected with sperm will fertilise. Embryos arising from the procedure, would then be transferred into the uterus of the woman.
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