Freezing of human eggs, also known as oocyte cryopreservation is the process of extracting and freezing human eggs to preserve them. When a woman desires to get pregnant the eggs are thawed and fertilized and the fertilized embryo is then inserted into the uterus.
It has long been possible to freeze and subsequently use male sperm successfully; even fertilized embryos were able to be frozen and reused, however it was not as easy to do the same with eggs (oocytes). This is because the freezing – thawing process tended to destroy the composition of the egg.
The egg is the largest cell in the human body and is made up of water mostly. When it is frozen, crystals of that water will form and damage the structure of the egg. This is why the success rate for developing viable embryos from frozen eggs was very low.
Now, however there are new technologies that involve very rapid freezing that have dramatically improved rates of producing viable embryos and successful pregnancies from frozen eggs.
The new technologies also use the process of dehydration of the egg prior to freezing, in order to obviate this problem of crystal formation that is seen to damage the egg’s integrity.
The process of freezing eggs or oocyte cryopreservation is an option for many women namely:
- If a woman is diagnosed with cancer, she may want to consider freezing her eggs. Prior to beginning radiotherapy or chemotherapy she may want to have her eggs extracted and frozen. Since cancer treatments produce radiation which is toxic to the eggs, a woman could choose to have them frozen for a future pregnancy. As many as 50,000 women in the United States who are of reproductive age are diagnosed with cancer each year, for whom this option could prove invaluable.
- Many women, for emotional, personal or professional reasons, because they do not yet have a partner or because their professional life does not permit it at the time, may choose to postpone motherhood. However, with age, the quality of eggs deteriorates and many women who apprehend early menopause and early depletion of eggs could opt to freeze their eggs.
- Many women, who may be undergoing treatment related to assisted reproduction, may have religious or ethical aversions to having embryos frozen. For such women as well, oocyte preservation may be a suitable option. For many, creation and then disposition of unused embryos creates an ethical and religious dilemma due to personal beliefs.