Freezing & Storage of Eggs
What is Egg Freezing?
Egg freezing is still a relatively new technique that allows eggs to be stored for a long time at temperatures below freezing point. In the UK 32 centres are licensed by the HFEA to carry it out, fewer than 10 centres offer it to patients at the moment.,
Who can have egg freezing?
Women facing medical treatment that may affect their fertility, such as chemotherapy, radiotherapy or surgical removal of the ovaries, may benefit from egg freezing. Also, women at risk of premature ovarian failure or suffering from endometriosis, cysts and pelvic infections could preserve their fertility by storing their eggs for later use. Egg freezing could also allow women who delay having a baby, due to career demands, the lack of partner, or pathologies that momentarily prevent pregnancy, another choice in family planning.
How are the eggs collected?
Fertility drugs are given to stimulate the ovaries to produce several follicles, sacs of fluid that hopefully contain eggs (see the leaflet “Ovarian Stimulation”). The development of follicles is monitored by vaginal ultrasound scans. When the follicles have reached the right size the eggs are collected by a clinician using a needle to remove the fluid within the follicles. This is done under ultrasound guidance. The fluid is looked at under a microscope and any eggs present are identified by the embryologist and placed in an incubator until they are frozen. Not all eggs are suitable for freezing. Only mature eggs will be frozen. [image-placeholder]
How are eggs frozen?
Eggs are frozen using a process known as cryopreservation, where the eggs are placed in a series of special solutions containing a cryoprotectant (antifreeze) and they are slowly cooled down in a controlled manner using a special freezing machine. Then they are placed in a storage tank containing liquid nitrogen.
How long are eggs stored for?
Eggs can, in theory, be stored for years and still be viable after thawing. According to the HFEA the usual period for storing eggs is 10 years which can be exceeded only in certain circumstances. A written consent is required for storing eggs before treatment commences. The consent can be changed or withdrawn at any time before treatment or before the eggs are used in research (if the research option has been selected).
What happens when I want to use my frozen eggs?
Frozen eggs can be used in a natural or stimulated cycle. Once the patient is ready to proceed with treatment, the eggs are removed from storage and thawed. Not all eggs survive freezing/thawing process. Viable eggs are inseminated with sperm using a technique known as Intracytoplasmic Sperm Injection (ICSI), which has been shown to achieve better fertilisation rates with frozen/thawed eggs. Fertilised eggs are cultured for 2-3 days and the best 2 embryos are replaced in the patient’s uterus. [image-placeholder]
What are the success rates?
Until recently, pregnancy rates from egg freezing procedures were very poor. Scientific advances have now made egg freezing a viable option for women. To date around 150 babies have been born world-wide as a result of treatments using frozen/thawed eggs. Success rates are approximately 10-15%, although too small a number of cycles have taken place for this percentage to be completely accurate.
Are there any risks associated with egg freezing?
Although human embryos have been successfully frozen and thawed for over 20 years, egg freezing has been more difficult. Early studies in animals suggested that freezing may disrupt the intricate structures within eggs, potentially leading to genetic abnormalities in babies born using frozen/thawed eggs. Current data indicate that there is no increase in birth defects or chromosomal abnormalities in children born from frozen eggs. Many healthy babies have been born following egg freezing/thawing, however this is a new procedure and may involve as yet unrecognized risks.
Any other questions?
If you have any other questions about egg freezing please speak to a member of staff.