Egg Freezing: Fertility Preservation (FP) & Commercial Donor Egg Banks
It is estimated that fewer than 3,000 frozen egg babies have been born since the first baby in 1984. By comparison, over the same time period, the transfer of frozen embryos has resulted in almost 2,000,000 babies. The process of egg freezing involves stimulating the woman’s ovaries with fertility drugs in order to have her produce multiple follicles/eggs and then extracting those eggs through ultrasound guided needle aspiration. The objective is to obtain about 15-20 eggs for freezing and storing. The fact is that eggs do not survive cryopreservation as well as embryos do. In fact the chance of each frozen egg, upon being thawed and then re-fertilized propagating a competent embryo that upon being transferred to the uterus of a young woman (<35y) will result in the birth of a baby, is about 6-8%. By comparison, each frozen blastocyst upon being thawed and transferred to the same woman, would yield about a 30% chance of a live birth.
Furthermore, many eggs do not survive the freeze-thaw and many of those that do survive, ultimately fail to fertilize. Moreover, of those that do fertilize, a significant percentage fail to progress to progress to the expanded blastocyst stage of development (regarded as being the ideal stage for ET). This serves to explain why women undergoing egg freezing are encouraged to undergo as many egg retrievals as are needed to allow for the cryostorage of 15-20 eggs. That is why depending on their age, women who elect to bank their eggs for fertility preservation (FP) are encouraged to undergo as many egg retrieval procedures as needed in to bank 12-20 eggs before having some degree of confidence, of ultimately being rewarded with a live birth. This number is even greater for women over 39y of age where the progressive increase in the incidence of egg aneuploidy translates into a shrinking percentage of harvested eggs being
In 2008, my associate, I and my associate, Levent Keskintepe PhD reported on the ability to identify and selectively freeze “competent” (euploid) eggs. We did so by extracting and karyotyping the 1st polar body of each mature (M2) egg and thereupon only freezing those that had precisely 23 chromosomes in both the polar body and the egg. We demonstrated that the subsequent transfer of embryos derived from the fertilization of such “competent eggs” would improve the baby rate per egg of 27% per frozen egg (a 3-fold improvement), a better than 80% post-thaw survival rate and a 60% birthrate following the transfer of 1-2 such embryos. Because this is a relatively costly process, it has failed to gain widespread acceptance.
Indications for Egg Freezing:
- Fertility Preservation (FP): This involves cryobanking eggs for future use. It has application in cases for:
- Declining ovarian reserve, the prospect of pending physiologic, surgical or radio/chemo-therapeutic ovarian failure
- In cases where there is a need (for whatever reason) to delay or defer childbearing
- Women/couples undergoing in vitro fertilization, who for moral, ethical or religious grounds are opposed to embryo freezing on.
A few words of caution: In my opinion women choosing FP, should freeze their eggs before they turn 35y of age, beyond which point the incidence of age-related egg aneuploidy begins to accelerate significant. Older women electing to undergo cryostorage of their eggs need to be alerted to the fact that the chance of subsequent success declines and that there is little merit in freezing eggs after the age of 40y. Most importantly it is necessary to always underscore the possibility that several egg retrievals might be necessary to accumulate enough eggs to make the process worthwhile. Finally, in my opinion, older women (>40y), especially those who also have diminished ovarian reserve, should seriously consider having embryos generated following fertilization PGS tested.
- Egg Donation.
Here, eggs from donors are cryostored and made commercially available to patients in need of such treatment. More and more couples are presently journeying abroad for egg donation to take advantage of lower cost IVF. Also, frozen egg banks, springing up all over the country, allow couples to select frozen eggs from an (often online) inventory of donors, the inference being that this offers an equally successful alternative and with much greater convenience and at lower cost. However, convenience factor aside, there is little (if any) financial benefit in using such banks. Moreover, pregnancy rates using fresh (non-frozen) eggs are about 25% higher than when frozen eggs are used.