CRYOPRESERVATION IS A SPECIAL PROCEDURE IN WHICH CELLS AND TISSUE CAN BE STORED FOR LONG PERIODS TO BE USED LATER AND IS A PART OF MOST IN VITRO FERTILIZATION PROGRAMS.
CELLS AND TISSUE ARE FROZEN AND STORED IN LIQUID NITROGEN AT -196° CELSIUS. THE TERM USED FOR THIS TECHNIQUE COMES FROM THE ANCIENT GREEK WORD ‘KRYOS’, WHICH MEANS ‘COLD’.
The process is chosen for reasons as varied as providing an additional chance for pregnancy, or saving embryos in the face of certain medical treatments.
Cryopreservation of Embryos (embryo freezing) is undertaken if there are surplus healthy embryos following transfer. A special freezing technique called vitrification is used for embryo freezing. This technique involves quick yet gentle freezing. Embryos are then placed in a cryobank and kept at -196 °C (-321 °F). Frozen embryos may be stored for a few decades.
Frozen embryos are gently thawed when required for transfer. They are used when the fresh embryo transfer was unsuccessful or when a sibling is desired after a previous success. The main advantage of cryopreservation of embryos is that it completely removes the necessity of hormonal hyper-stimulation of the ovaries.
After hormonal stimulation, eggs may be removed from the ovaries and frozen. This procedure is recommended to young women who are about to undergo an oncological treatment but it is available to any woman wishing to preserve her eggs for later use.
Sperm may be frozen for a number of reasons:
- As part of a sperm donor scheme
- To preserve healthy sperm before oncological treatment
- For couples waiting for donor eggs
- As a backup in case a fresh sample is unable to be produced on the day of egg retrieval