Deep-freezing embryos has been routine for some time, to give infertile couples reproduction choices in various situations, but freezing unfertilized eggs has proven difficult.

Now, new research by an Italian team suggests that egg preservation in cold storage may in fact become be a feasible alternative to embryo storage. Still, improvements are needed, as the majority of eggs do not survive the freezing process.

The findings, which appear in the medical journal Fertility and Sterility, are based on a study of 68 couples being treated for infertility. Eggs were retrieved from the woman and frozen, either because the couple did not want “spare” embryos to be created, or because sperm was not available for fertilization at the time of retrieval.

A total of 86 thawing cycles were performed involving 737 stored eggs. Only 37 percent of eggs survived freezing and thawing, Dr. Andrea Borini, from Tecnobios Procreazione in Bologna, and colleagues report.

A little less than half of the viable eggs were fertilized, and most of these began dividing normally, the team reports. After implantation, fifteen women became pregnant, and ultimately a total of 13 infants were born - 5 boys and 8 girls.

With current slow freezing methods, most eggs will not survive and this is clearly an area that needs improvement, the investigators state. “However, it appears that (eggs) that are able to survive freezing and can be fertilized, allow preimplantation development and implantation with acceptable rates,” they add.

SOURCE: Fertility and Sterility, September 2004.