What is Egg Freezing
Egg freezing (Vitrification) is still a relatively new technique that allows eggs to be stored for a long time at temperatures below freezing point.
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 that 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. 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, under sedation. 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.
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.
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.
What are the success rates
The UK national average live birth rate from egg freezing is currently about 10%. However newer techniques in vitrifying the eggs are very promising. The live birth rate also depends on the age of the woman at the time of egg collection. It is estimated that if a woman stores 8 – 12 eggs before her thirties she will expect a 40% chance of having a baby when she decide to use her eggs.
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. 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.