With the fast-paced lifestyles and time-consuming jobs that many women are committed to these days, it seems that more and more women are trying to have children only to find out that it is "too late." Recent advances in medicine now allow women the potential opportunity to delay their pregnancy until a more opportune time (“the right time”). The "right time" may mean the right partner, the right place in the right career that allows for the investment of more time to a family, or even the right state of health. When the “right time” comes, regardless of the intense desire to have a baby, there is unfortunately no guarantee that a woman will be able to have a genetic child.
Even with all the technology that we as physicians specializing in Reproductive Endocrinology now have available through IVF, treatment can only increase chances of conceiving but not guarantee it. The is particularly true if a woman chooses to delay childbearing past the age of 35. There is, in fact a biological clock, and a woman’s fertility quotient does decrease as she gets older . Unlike men who produce new sperm every day of their reproductive lives, women are born with all of the eggs that they are going to have. As a woman ages her eggs decrease in both quantity and quality as well.
Many women struggle with this concept. After all no one would call a 35 year old women old and in fact at age 35 a woman has most likely lived less that one half of her life since a woman’s average life expectancy is currently more than 82 years. “Mother Nature”, on the other hand, still “thinks” that a 35 year old women is not likely to live past the age of 50 and it would seem, therefore, that she has no interest extending a woman’s reproductive life span beyond what it is today. As a consequence, not only does a woman’s fecundity rate ( the chance of pregnancy in any single Cycle) decline as she gets older but her chance of miscarriage increases as well as reflected in the 2 graphs below.
Wouldn’t it be wonderful, therefore, to be able to offer women an opportunity to get older without experiencing a significant decrease in their ability to conceive? For decades, science has allowed us to freeze sperm and for years we have been able to freeze embryos, but only just recently have we been able to freeze eggs. Numerous studies have been reported in search of developing an ideal oocyte cryopreservation method after the first report of a successful pregnancy using a frozen thawed oocyte in 1986. Since that time several centers around the world have reported similar success. Most of these pregnancies were achieved by a slow-freezing method. The survival of oocytes following thawing after this slow-freezing technique has been very low, as have pregnancy rates. Therefore there has been a pressing need to develop a more efficient way to cryopreserve oocytes. Such a protocol must reduce the damage to cells caused by ice crystal formation during the freezing process.
At the present time Vitrification offers the best solution to the problem. Vitrification is a very simple procedure and requires no programmable freezing equipment. In the process of vitrification an oocyte is placed in a very small volume of vitrification medium and is then cooled at an extremely rapid rate. The fast freezing eliminates the formation of ice crystals in the oocyte. Subsequent to the vitrification, the oocyte is stored in liquid nitrogen until such time as it is to be thawed and fertilized.
Vitrification protocols are starting to enter the mainstream of human ART and have been used successfully since 1999. Successful pregnancies following the use of this technology are being reported with greater frequency. To date a “universal” vitrification protocol has not been defined however research towards this end continues and will no doubt lead to higher levels of clinical efficiency as well as utilization. To date the most impressive studies quote survival rates and Fertilization rates of 68.6% (325/474) and 71.1% (142/198) respectively. In this same study pregnancy rate and Implantation rate per Embryo transfer were 21.4% (6/28) and 6.4% (8/125) respectively. In 2 more recent studies (the first published and the second unpublished) pregnancy rates have been reported as 56.5% (13 pregnancies/23 patients) and 75% (3 pregnancies/4 patients). Clearly these numbers are small but they do hold great promise for the efficacy of this technology. To date of the approximately 200 children born using this technology (2/3 using slow freezing and more recently 1/3 using vitrification) only 1 Congenital abnormality has been reported.
Clearly the feasibility of vitrification of human oocytes has been confirmed. It is important to note, however, that because the numbers are still very small, the American Society for Reproductive Medicine (ASRM) considers egg freezing investigational unless it’s being done as a heroic measure for women who may risk loosing their reproductive function as a consequence of surgery or chemotherapy for cancer. Nevertheless the procedure is being offered electively by several reputable Infertility practices without IRB approval and is even being promoted and advertised by a newly formed company created solely for the purpose of offering egg freezing to women who wish to electively attempt to preserve their reproductive function as they get older.
-Courtesy of FCI
For more information on vitrification, visit The Fertility Centers of IL website.