Treatment - Egg Freezing
For more than fifteen years, IVF laboratories have been able to successfully freeze human embryos (fertilised eggs) and generate pregnancies that result in healthy live births.
However, the freezing of mature human eggs has proven technically difficult.
These difficulties have been mainly due to the dynamic nature of the maturing human egg itself. Many of the structures within the egg, are still finalising their maturation, so that successful fertilisation can occur. The actual size of the human egg has also presented technical difficulties, as it is one of the largest cells in the human body.
This has meant that complete penetration of the egg, by the molecules that prevent ice crystal formation during the freezing process, has been difficult to achieve. In the past when an attempt to freeze eggs has been made, the egg would often burst as ice expanded, or damage would occur to the internal structures of the egg as ice crystals formed.
At this stage, egg freezing at IVF Sunshine Coast is viewed as a developmental technology and not yet a tried and proven protocol.
Who may benefit from egg freezing?
Age and deferred childbearing have become one of the most common reasons for couples presenting to fertility clinics. Many women are delaying marriage or going on to develop their careers and as a result, delaying having a family.The clinical difficulty that this presents is that human fertility is very age dependant. 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.
A woman may however, choose to freeze her eggs while she is still young, if she does not have a partner or is not wanting to have a baby at that time.
The use of mature egg freezing, therefore makes it possible for women to develop their careers and relationships, with the improved likelihood of successful reproduction, at a time that is right for them, and not necessarily when the female body clock determines.
How Will the Oocytes be Collected?
A woman embarking on freezing her eggs would need to go through a conventional cycle of IVF ovarian stimulation, with hormones designed to recruit several eggs, rather than the one egg that is ordinarily released per cycle.
The oocyte retrieval procedure is done in Theatre under an anaesthetic and on average, 10 eggs are collected per stimulation cycle. Women can expect to leave hospital a few hours after the egg collection.
More information about the drugs used in the ovarian stimulation, their risks and side effects as well as IVF overall, is available from IVF Sunshine Coast.
How Will the Eggs be Frozen and Stored?
The eggs are placed in individual plastic straws in a liquid designed to protect them from damage by ice crystals as they are frozen.
The straws containing the eggs are frozen and 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 Could the Frozen Eggs be Used?
When the frozen eggs are required they would be thawed 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). The information sheet available from IVF Sunshine Coast on ICSI has more detailed information on this procedure and should be consulted.
Using currently available freezing and thawing procedures, around 60% of frozen oocytes, injected with sperm, will fertilise. This is similar to the fertilisation rate achieved with fresh oocytes (eggs) in the IVF program.
Embryos arising from the procedure, would then be transferred into the uterus of the woman.
At this point in time, the clinic at the University of Bologna in Italy is reporting pregnancy rates for embryos from frozen eggs, that are very similar to results achieved using fresh eggs. They have now established in the order of 70 or 80 clinical pregnancies using frozen eggs.
The Potential for Failure of the Procedure
This procedure is under continual development, and like all assisted reproductive technologies, has the potential for failure in a number of ways.- None of the oocytes may survive the freeze/thaw process. This is more likely to occur if the number of oocytes frozen is low. None of the thawed oocytes may fertilise despite having sperm injected into them. This is more likely to occur if the number of thawed oocytes for sperm injection is low, or if the sperm used is very poor quality. No pregnancy results from the transferred embryos.
- A pregnancy may not be ongoing, ie may result in a miscarriage or an ectopic pregnancy. Unfortunately, this outcome is a potential for any human pregnancy, whether or not Assisted Reproductive Technology is employed.