Egg freezing might be an option if you’re not ready to become pregnant now but want to try to make sure you can get pregnant later.
Egg freezing doesn’t require sperm, but you’ll need to use fertility drugs to make you ovulate so that you’ll produce multiple eggs for retrieval.
You might consider egg freezing if:
Before beginning the egg-freezing process, you’ll likely have some screening blood tests, including:
You’ll take synthetic hormones to stimulate your ovaries to produce multiple eggs.
An ultrasound probe is inserted into your vagina to identify the follicles. A needle is then guided through the vagina and into a follicle. A suction device connected to the needle is used to remove the egg from the follicle.
Shortly after your unfertilized eggs are harvested, they’re cooled to subzero temperatures to preserve them for future use.
The process most commonly used for egg freezing is called vitrification.
When we freeze cells in a lab, the main focus of the process is avoiding ice crystal formation. An ice crystal is razor sharp and will readily shred any cell membrane, killing the cell. As water in the cell turns to ice, it expands in volume, rupturing (killing) the cell.
First, eggs are exposed to high concentrations of cryoprotectants to allow rapid dehydration of cells. Then they are quickly loaded into straws and plunged into liquid nitrogen at a temperature of -196°C. The tiny straw will cool from room temperature (about 25°C) to -196°C in 2-3 seconds giving a cooling rate of 4420 to 6630°C/minute.
This high cooling rate combined with the use of high concentrations of cryoprotectants allows the contents of the straw (embryos plus surrounding fluid) to turn to a glass like substance instead of ice. Avoiding ice formation in this way successfully protects the embryos from damage and allows them to be warmed later giving survival rates consistently above 90%.
When the woman is ready to use the frozen eggs to achieve pregnancy, these cryopreserved eggs are placed in warming solution and assessed. Those eggs that survived the freezing process are fertilized with intracytoplasmic sperm injection (ICSI), and the fertilized eggs will grow in culture until the embryo(s) are ready to be transferred into the uterus to achieve pregnancy.