Freezing & Storage of Eggs
What is egg freezing and why do it?
Egg freezing is a relatively new technique that allows mature eggs to be stored for a long time at very low temperatures. The eggs are cryopreserved using the ‘vitrification’ method (also known as fast freezing) before they are stored in liquid nitrogen at -196°C until they are going to be used. The eggs can then be stored for up to 10 years. In some cases the storage period can be extended beyond 10 years, but this is not true for everyone.
Egg freezing is used for both social and medical reasons. Many women are now waiting until later life before trying to have a baby, this however presents a number of challenges. Egg freezing can overcome some of these challenges by giving women the opportunity to retrieve and store their eggs whilst they are younger, during their prime reproductive years. The eggs can then be used later in life during a cycle of ICSI treatment to help achieve a pregnancy. Other women may decide to freeze their eggs for medical reasons.These women may have experienced premature ovarian failure, undergone surgery to remove their ovaries or needed chemotherapy or radiotherapy to treat cancer. All of these things will affect your fertility, meaning that egg freezing could help you in the future to achieve a pregnancy.
What is involved in freezing my eggs?
To maximise the chances of freezing eggs successfully, the ovaries are stimulated using daily fertility drugs. This encourages them to produce more than one follicle during the stimulated cycle. The egg itself is growing within the follicle. Pelvic ultrasound monitoring is used to check the ovaries and to see how many follicles might be developing. Blood tests may also be needed to check the hormone levels in the body.
When at least 3 follicles measuring more than 17mm in diameter are seen, a hormone injection is given to ripen and mature the eggs. Egg collection is then carried out under sedation approximately 36 hours later. This procedure takes about 20 minutes and involves removing the fluid from each follicle. The embryologists then examine the fluid under the microscope to see if an egg is present. Eggs are then checked to see if they are mature or not. Not every egg is mature when they are collected. All mature eggs are ready to receive a sperm cell and are cryopreserved using the fast freeze or vitrification method.
What happens when I want to use my eggs?
When you decide you want to use your eggs you will need to undergo an ICSI treatment cycle. Find out more about ICSI. At the appropriate time the eggs will be thawed and it is important to note that not all eggs will survive the thawing process. These eggs are then fertilised by injecting the sperm into the egg.
What are the outcomes using frozen eggs?
As egg freezing is relatively new there is a not a huge amount of data on risks and success rates. Research has not shown any link between using a frozen egg for treatment and giving birth to a baby with a birth defect or chromosomal abnormalities. The chance of having a live birth using a frozen egg is currently around 15%.