Freezing of human embryos has been a routine procedure since the early 1980s. Conventional techniques (which are still being widely used by many ivf centers), involve slow freezing, which unfortunately can result in ice crystal formation inside the cell(s), damaging them and reducing embryo “competency” (the subsequent ability upon thawing, to propagate a viable pregnancy). The introduction of ultra-rapid freezing or vitrification has revolutionized this process. This innovative technology rapidly freezes the cells (literally within seconds), thereby preventing intracellular ice from forming and preventing cell damage. As such, vitrification is a major advance in art. Now, for the first time, egg freezing can be performed with minimal risk of failure. The door has been opened to the freezing of human eggs, with the expectation of much improved success rates over those that were possible using prior conventional freezing methods.
Vitrification involves rapid freezing of the eggs in a tiny straw of a special vitrification solution, before storing them in liquid nitrogen. When compared to the older conventional slow freezing methods survival rate for human embryos of about 75-80%, vitrification improves post-thaw (warming) embryo survival to >90%. Reports indicate that survival rates of frozen eggs using vitrification also approximate >90%. Vitrification technology has opened up new horizons for medically assisted reproduction.
Once the eggs are frozen, they may be banked for long periods of time. At the present time, we do not know how long; extrapolating from the information we have from frozen embryos, we have every reason to believe the eggs could be frozen for many years (in excess of 10 years) and subsequently successfully thawed with resulting fertilization and pregnancy initiation.
A question that frequently comes up is whether there is an increased risk of congenital malformations from pregnancies resulting from these procedures. Again extrapolating from what we know about frozen embryos, the incidence of birth defects is the same as in the population at large (~ 1%). Studies are continually being done to evaluate this more comprehensively and those of us involved in this work are required to report incidents of birth defects, so if there is any problem in this regard, it will rapidly become known.
Another question that is frequently asked is whether undergoing the procedure for egg donation will somehow result in infertility or an earlier onset of menopause. With respect to the former question (infertility), it is important to realize that a full infertility evaluation is not performed on those women presenting for egg donation. For example, if a 20 year old woman presents for egg freezing for donation, since she is not going to be conceiving at that time, there is no point in doing an invasive hysterosalpingogram to document tubal patency. Accordingly, it may be that her tubes are blocked and it is not the procedure of egg donation which caused it. However, assuming there is no such problem in the tubes or ovaries, the process of ovarian stimulation and egg donation should leave no long term effects. Furthermore, since the woman is destined to lose those eggs she is donating in the given month regardless of whether they are donated via egg freezing or not, this process should have no impact whatsoever on the onset of menopause. That is a genetically predetermined situation and barring disease or surgical castration, it will occur at the time dictated by genetics (average age of menopause in the western world is 51.4 years).