Vitrification (similar to freeze drying) proves to be successful world wide
At the October 2012 American Society for Reproductive Medicine meeting, oocyte cryopreservation (“egg freezing”) was declared to be standard fertility practice, and no longer considered experimental.
Those of us who have been practicing fertility medicine for decades were particularly gratified by this development. This “closes the loop” of reproductive options for women, and for couples who desire to limit the number of embryos generated in their IVF cycle.
Freezing of reproductive cells has been practiced for many years, for both human and animal species such as cows. Much of what we know about freezing human sperm and embryos was first used for other species and then adapted for humans.
The human oocyte (“egg”) has been difficult to freeze, though, because it is a large cell and the genetic apparatus is very vulnerable. This means that if there is damage from the freeze or warming, the egg may not fertilize properly and make a normal embryo.
Various freezing approaches have been tried over the last decades, but no procedure was giving consistent egg survival rates. Recently a technique called vitrification, similar to freeze drying, has proven to be very consistent in the hands of embryologists all over the world. For this reason, the procedure is no longer considered experimental.
Who might need this? The most obvious group is women who will be undergoing radiation, chemotherapy or removal of the ovaries for cancer and a variety of other medical conditions, and who don’t have a male partner (if a woman has a partner, freezing embryos is recommended in most cases). After she has recovered from her disease, if she no longer has good egg production, the cryopreserved eggs can be thawed and used to conceive.
Other women may know that their career or social path means they will not be trying to conceive until their later reproductive years. These women may choose to freeze their eggs in their 20’s or early 30’s.
Sometimes a couple may not wish to produce more embryos than can be used in a single IVF cycle. They may wish to limit the number of eggs placed with the sperm for fertilization, and freeze the remainder. Rarely, in the midst of an IVF cycle, sperm is not available due to illness or unforeseen circumstances. The eggs can then be frozen for later insemination.
Lastly, the area of egg donation has been a gratifying option for many with diminished ovarian function, or genetic disease. But fresh egg donation holds many challenges. Having banked cryopreserved eggs available, often at lower cost, may open doors for more women.