Egg Freezing - Coming of Age
Egg Freezing For Diminished Fertility Associated With Age
While we have had the ability to freeze human embryos (fertilized eggs) successfully since about 1984, it is only in the past decade that we have gained the technology needed to successfully freeze human eggs with good clinical outcomes. The technology which proved successful for freezing embryos, specifically slow freezing, resulted in poor outcomes when applied to the cryopreservation of eggs. One of the main reasons this technique proved unsuccessful has to do with freezing damage to the delicate interior part of the egg called the spindle fibers. In the past decade application of rapid freezing called vitrification has resulted in substantially improved egg survival, fertilization, and cleavage of early stage embryos. In fact, vitrification of human eggs has been shown to result in survival rates and clinical outcomes similar to fresh eggs.
This technology represents a powerful tool when used for either medical or elective reasons. Medical reasons would include preservation of eggs for a woman who must undergo radiation therapy or chemotherapy for cancer treatment, while elective reasons would refer to prevention of future age related infertility problems. Some have referred to this as “social egg freezing”. Those of us who practice in the field of reproductive medicine have long understood the difficulties in successfully treating age related fertility. Even the most sophisticated treatment, in-vitro fertilization, has not proven to be as successful as we had hoped for management of age related infertility. We have learned that the cause of age related infertility is clearly traced back to the egg, likely due to a combination of chromosomal and cytoplasmic factors. In the future it may become commonplace for women who are 30-35 years of age and not ready to conceive for either career or social reasons, to go ahead with one or two cycles of egg freezing with the intentions of freezing and preserving approximately 20-30 of their eggs. Studies done to date using vitrification to freeze oocytes have suggested that each egg represents a 5% possibility of a live birth. Typical egg retrieval procedures done today in the United States result in the removal of 10-15 eggs, therefore it is reasonable to conclude that completion of two egg retrieval procedures would provide an excellent prospect for a successful pregnancy at some time in the future.
While vitrification of eggs is currently being done throughout the world, it is still considered experimental in many countries including the United States. Israel’s National Bioethics Council recently approved freezing of eggs for medical and elective purposes, which many perceive as movement in the direction of accepting egg freezing as non-experimental. Most agree that studies looking at the health and development of children conceived through the use of vitrified eggs must be done to assure the safety of this treatment.
Source: Fertility and Sterility, Vol. 96, No. 2, August
