New clinical guidelines for egg freezing in the UK
3 November 2009
The British Fertility Society (BFS) and Association of Clinical Embryologists (ACE) have issued new guidelines in the journal Human Fertility on the effectiveness and safety of egg freezing for medical purposes. These guidelines follow a thorough review of published research on different technologies used in egg freezing and present a number of recommendations to UK clinics as follows:
- Egg freezing is an emerging technology with promising initial results. The value of egg freezing is currently limited by several factors including the number of eggs that can be obtained and the success rates achieved. There is a need for further large scale properly controlled clinical trials to improve our knowledge base of the most effective techniques.
- Women considering freezing eggs should be provided with accurate information on safety and likely success rates and given appropriate counselling. Guidance should be given on both the benefits and limitations of egg freezing compared to other options. Currently, greater success is likely via embryo, rather than egg storage, if circumstances allow.
- There are two main methods to freeze eggs: slow cooling and vitrification. Initial studies indicate that vitrification may produce higher success rates than slow cooling. More studies are needed to confirm the optimum composition of chemicals used to freeze the eggs in and the long-term safety and efficiency of vitrification.1
- For best results, mature eggs should be collected following ovarian stimulation, similar to IVF treatment. The type of ovarian stimulation used should be dictated by the needs of each patient. For example, women with hormone sensitive cancers may prefer treatments that minimise exposure to oestrogen.
- Studies suggest the fertilisation of thawed eggs is more successful using ICSI (where one sperm is directly injected into one egg) rather than conventional IVF techniques (where sperm and eggs are incubated together in a ratio of approximately 75,000:1).
- There may be clinical situations where freezing immature eggs is necessary. Immature eggs can be removed without stimulating the ovaries. But, further research is needed to identify the best methods of freezing and then maturing them in vitro when thawed.
Both the BFS and the ACE support egg freezing as a technology of preserving the fertility of women facing future infertility because of surgery, chemotherapy or radiotherapy, but not as a solution to counteract age-related fertility decline.
Prof Adam Balen, Chair of the British Fertility Society Policy & Practice Committee, said:
“The British Fertility Society wants to ensure that all women receive the safest and most effective treatment when undergoing fertility procedures. Following a thorough review of the literature, these guidelines aim to provide our members with evidence-based information on the safest and most successful technologies to use in egg freezing.
“At all stages of discussions, patients should be given clear information on their options and counselling on both the benefits and limitations of egg freezing. Current success rates achieved using eggs that have been frozen are relatively low, with the live birth rate per thawed egg at approximately 2-3%. It is essential for more research to be carried out in this area to develop the techniques used and improve the safety and efficiency of egg freezing. This research should also be combined with comprehensive follow-up studies of any resulting children.”
Mrs Rachel Cutting, from the Association of Clinical Embryologists, said:
“Egg freezing is a relatively new treatment which offers promising initial results. Although research in this area has moved forward considerably in the last few years, we still need to know more. We would like to see more robustly designed clinical trials to inform us on the best techniques to use in the laboratory to increase egg survival and lead to more successful pregnancies. The Association of Clinical Embryologists is committed to promoting the highest standards of practice and we look forward to working with the sector to improve the success of egg freezing techniques.”
General information
The process of egg freezing involves removing eggs from a woman’s ovaries, which are then frozen for storage. At a later date, these eggs can be thawed, artificially inseminated and introduced back into the patient's womb, with the intent of creating a successful pregnancy.
All techniques used to freeze eggs aim to minimise the formation of harmful ice crystals in the eggs during cooling or warming while also minimising any detrimental effects of the cryoprotectants (chemicals that protect eggs from freezing damage). There are two main techniques: slow cooling where eggs are frozen slowly using lower concentrations of cryoprotectants and vitrification where eggs are frozen quickly using higher concentrations of cryoprotectants.
These guidelines will be reviewed in June 2013.
Notes for editors:
1 The American Society for Reproductive Medicine Practice Committee (2007) stated that a live birth rate per oocyte thawed should be quoted as 2% for slow freezing and 4% for vitrification, although these figures may be conservative as technology has improved since these data were published.
For more information, please contact the British Fertility Society press office
References
This report is published in Human Fertility 2009, 12(3), 125-136. DOI: 10.1080/14647270903132115. Human Fertility is the official journal of the British Fertility Society.
The British Fertility Society is a national multidisciplinary organisation representing professionals practising in the field of reproductive medicine. The British Fertility Society is committed to promoting good clinical practice and working with patients to provide safe and effective fertility treatment. For general information, see: http://www.fertility.org.uk/
The Association of Clinical Embryologists was founded in 1993 to promote high standards of practice in clinical embryology and to support the professional interests of embryologists working in the UK. For general information, see: http://www.embryologists.org.uk/