Egg cryopreservation, preserving eggs by cooling to sub-zero temperatures, includes freezing eggs which first took place in 1986. Since then, over 500 children worldwide have been conceived from frozen eggs.
Vitrification is an alternative to egg freezing, first applied in humans in 1999. The process involves cooling cells to form an ice-free transparent glass. Since this process was first used, there have been well over 450 births reported.
The review adds that vitrification can be simpler, more efficient and cheaper than conventional freezing under certain circumstances. It is quicker than freezing for a small group of eggs collected from a single donor, whereas freezing may be more efficient when eggs are to be stored for several women on the same day. Expensive cooling apparatus is not required but vitrification consumables are currently expensive and embryologists may have to devote more time to vitrification than freezing.
As the application of vitrification for human egg storage is comparatively recent, there is no certainty that there are no short or long-term implications for the children conceived from vitrified eggs. The same is true for frozen eggs. Nevertheless, the review states that among 392 children developed from vitrified oocytes, only six birth anomalies were identified; an incidence that does not differ from that in natural conception.
The review concludes that vitrification is promising and can conserve egg competence for fertilisation and development at a level similar to that of freshly collected eggs. However there have been too few live births reported following this process to realistically assess the efficiency of vitrification.
As this method becomes more widespread the long term health of the children can be assessed as well as the methodology and safety of storage.
Dr Maureen Wood, Honorary Research Fellow, Department of Obstetrics and Gynaecology, University of Aberdeen and author of the review said:
“Vitrification is a novel and very exciting method of preserving eggs. For example it gives women at risk of early ovarian failure more confidence to store their eggs in the hope of later bearing their own genetic children. Already it is facilitating the management of donor egg banks and allowing a quarantine of donated eggs comparable with that required for donated sperm.
“However there is scope for further development of the procedures and more research is needed to assess its full potential including the longer term outcomes.”
TOG’s Editor –in-Chief, Jason Waugh said:
“This review looks at the advantages and disadvantages of this relatively recent technology. It is very promising for women who may look to this for safeguarding their chances of future childbearing.
“However, as it becomes more widespread globally, more research needs to be done to further our understanding of it.”
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The Obstetrician & Gynaecologist (TOG) is published quarterly and is the Royal College of Obstetricians and Gynaecologists’ (RCOG) medical journal for continuing professional development. TOG is an editorially independent, peer reviewed journal aimed at providing health professions with updated information about scientific, medical and clinical developments in the specialty of obstetrics and gynaecology.
Wood MJ. Vitrification of oocytes. The Obstetrician & Gynaecologist 2012;14:45–49.