Over the past 25 years, reproductive endocrinologists have had good success freezing embryos (fertilized eggs) but very poor success freezing unfertilized eggs. However, in order to fertilize an egg (oocyte), one must have sperm available. In the past we have cared for many single women who are comfortable getting pregnant with anonymous donor sperm because they are getting older and running out of time. Women are born with all of their eggs. The biological clock keeps ticking. A woman’s fertility decreases after age 35 and is dramatically reduced after 40 (often requiring donor egg). The newer technology (vitrification) for successfully freezing unfertilized eggs is a major improvement over previous techniques and allows women more options.
The survival of eggs following the older, slow-freezing technique has been very low, as have pregnancy rates, often due to damage to the egg cells caused by ice crystal formation during the freezing process. Vitrification involves a better flash- freezing technique where the delicate egg, once unfreezable without damage, can now be safely preserved for future use. In the process of vitrification, an oocyte is placed in a small volume of the vitrification medium and is then cooled at an extremely rapid rate. This fast freezing eliminates the formation of ice crystals in the eggs. Following this freeze, the egg is stored in liquid nitrogen until such time as it is to be thawed and fertilized by a sperm.
There are several indications for egg freezing (Vitrification or Cryopreservation) including:
The American Society for Reproductive Medicine (ASRM) no longer considers oocyte freezing investigational. Fertility Centers of Illinois (FCI) is one of several IVF programs nationwide approved to perform vitrification of eggs.