New technology allows women to preserve their eggs for use later

Jun 20 2006

Japanese scientists have come up with a new method of preserving human embryos which will make the process of freezing them safer and more reliable.

The new and highly successful method of freezing human eggs will make it easier for women to preserve their eggs as men are able to do for use at a later date.

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 says the method 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.

The method also represents a realistic option for the preservation of fertility in women who are in need of aggressive treatment for malignant diseases.

Dr. Kuwayama says that although sperm can be frozen, thawed and used for in vitro fertilisation with high levels of success, the freeze-thawing process can damage eggs and, until now, it had been very difficult to perform successful IVF using frozen-thawed eggs.

Researchers say that worldwide less than 150 babies have been born using eggs that have been frozen.

By using the Cryotop method many of the problems of human oocyte cryopreservation are resolved and a more than 90% survival rate was achieved for the freeze-thawed oocytes.

A high pregnancy rate of nearly 42% occurred after the oocytes had been fertilised and implanted in the women which equals that achieved using fresh oocytes.

The Cryotop method involves very rapid freezing in a tiny amount of a special vitrification solution, before storing in liquid nitrogen.

This process prevents ice crystals forming, which damage the structure of the egg.