The research, presented today (Monday 19 June) at the 22nd annual meeting of the European Society of Human Reproduction and Embryology, gives hope to hundreds of women who want to preserve their future fertility but who, for whatever reason, only have eggs, not embryos, available for freezing.
Dr Masashige Kuwayama told a news briefing that although sperm could be frozen, thawed and used for in vitro fertilisation with high levels of success, the freeze-thawing process could damage eggs and, until now, it had been very difficult to perform successful IVF using frozen-thawed eggs. Research by Professor Stefania Nottola and Dr Sandrine Chamayou, presented at the conference, gave examples of the current problems of conventional freeze-thawing and the need for more effective techniques. It is thought that worldwide less than 150 babies have been born using eggs that have been frozen.
Dr Kuwayama, scientific director of the Kato Ladies Clinic in Tokyo, Japan, has developed a new method of freezing eggs (oocytes) called the Cryotop method, which he first used for artificial insemination in sheep and cattle.
He said: "The Cryotop method is a highly efficient freezing procedure that opens a new way to resolve the various aspects of the problem of human oocyte cryopreservation. Using this method, we achieved a more than 90% survival rate for the freeze-thawed oocytes and a high pregnancy rate of nearly 42% after the oocytes had been fertilised and implanted in the women. This pregnancy rate is practically the same as the rate we can achieve in our clinic using fresh oocytes."
The Cryotop method involves very rapid freezing in a tiny amount (less than 0.1 microl
Source:European Society for Human Reproduction and Embryology