Cryopreservation is a technique which may be used to freeze eggs or embryos for later use in an in vitro fertilization (IVF) cycle. When the eggs or embryos are needed, each are carefully thawed. Embryo cryopreservation means that a woman does not need to undergo multiple rounds of ovulation stimulation for another cycle of IVF.
Freezing eggs, also known as oocyte cryopreservation enables women to conceive a child at a later date. This is an option that women may choose if pregnancy is not an option now but may be in the future. For example, a woman may be currently undergoing cancer treatment or may wish to freeze eggs while still young for use later.
Hormone therapy is used to stimulate the production of mature eggs. The eggs are then harvested and frozen for later use. A frozen egg can be thawed whenever an egg is needed. Women can use frozen eggs to become pregnant with sperm from a partner or from a sperm donor. The embryo can then be implanted in the woman’s uterus.
When fresh eggs have been harvested, or frozen eggs have been thawed, these may be fertilized in a laboratory using a man’s sperm. If the woman does not wish to use the embryo immediately, or if more embryos have been created than can be transferred to the woman’s uterus, the embryos may be frozen. Embryo cryopreservation allows a woman to have another embryo transfer without having to go through another full IVF cycle.
Embryos can be frozen at any point between day one and six following egg harvesting. Unfortunately, not all embryos are in a viable condition to be frozen. Great care is taken to protect frozen embryos and minimize the possibility of damage. Typically, between 60-90% of frozen embryos survive the thawing process. After the transfer of thawed embryos, the chance of a successful pregnancy is the same as that of a fresh embryo. Frozen embryos may be stored for several years; the embryo’s viability remains the same as those frozen for just a few months.
Cryopreservation can be useful for young women who don’t want to start a family yet, but may want to in the future. This procedure can also benefit women who are currently undergoing certain types of medical treatment. Women who wish to freeze eggs or embryos for later use should talk to a fertility specialist.