Cryopreservation of oocytes, while not a new process, has only recently become available for fertility preservation. The use of this practice in male fertility has been utilized for years; the first recorded human birth from cryopreserved sperm was in the 1950s. It was only two years ago that the American Society for Reproductive Medicine lifted the experimental ban on egg freezing, allowing clinics across the country to offer this procedure to their female patients.
Cryopreservation is the slow freezing of cells or tissue to preserve their current state for future use. It involves freezing tissue in liquid nitrogen at -148 degrees Fahrenheit, suspending animation and halting the natural occurrence of decay. The metabolic process of tissue slows downs immensely when it is subject to extreme cold, making cryopreservation a helpful tool by allowing tissue and cells to be stored for long periods of time. When used for egg freezing, this process allows women to pause the inevitable aging process of fertility.
The only drawback of cryopreservation is the increased possibility of ice crystals forming, expanding the cells and potentially causing cell death. Vitrification is the new and improved egg freezing process that allows cells to be flash frozen, removing the possibility of water interfering in cell quality. This has helped increase thawing success, allowing 80-90% of eggs frozen using this process to be viable, even years later. While vitrification is the preferred method of freezing, many clinics still find their best results utilizing cryopreservation.