The cryopreservation or egg freezing is a procedure which is specialized for a select group of patients.
One type of patient who will use this service is the woman who has the desire to preserve her fertility. Often, this is a woman who is not married and is in her mid to late 30’s. The unavailability of a partner’s sperm, the reluctance to use donor sperm and the diminishing number of eggs in her ovaries may lead a woman to choose to freeze some of her eggs for use at a later time.
Another type of woman who chooses to freeze her eggs is a woman facing medical treatment for a disease, such as cancer, which could jeopardize her chances of producing healthy eggs. If she also does not have a partner, freezing her eggs may the best option for her.
In both cases, the patient receives a fertility drug administered by her physician in order to stimulate her ovaries to make several eggs. When the follicles have matured, the patient will be given an injection of the hormone that provides the final maturation of the eggs.
The egg retrieval will occur 36 hours later. The eggs will be washed and then graded for their maturity. All of the healthy, mature eggs will be cryopreserved within two hours of their retrieval. The eggs that are very immature at retrieval are incapable of being fertilized and they do not continue developing if they are frozen. Since they have no chance of producing an embryo, these eggs are discarded. However, the eggs that are very close to maturity may continue to mature even if they are frozen at this time. So, these eggs will be cryopreserved separately and labeled accordingly in order to get as many eggs as possible from the retrieval.
When a patient is ready to have her eggs thawed, she must have a source of sperm in order to accomplish fertilization and produce embryos. This sperm source can be her partner or frozen donor sperm. Since the egg retrieval has been performed, there will be no need for the ovulatory medication. Instead, the patient will begin to prepare her uterus for the embryo transfer. When the uterine lining is ready, the eggs will be thawed by the embryologists in the lab. The eggs that survive the thawing process will be injected with sperm (ICSI). The following day, the eggs will be checked for fertilization. All of the fertilized eggs will be placed in a medium that will support their growth. They will be examined again on day 3 for growth and the physician will be notified. The physician will decide if the transfer will occur on day 3 or on day 5 and the patient will be notified.
The viability of the eggs is not affected by the length of time that they are frozen.