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Egg Freezing for Fertility Preservation: An Update

For several years now, Pacific Fertility Center has been a leader in freezing of blastocyst-stage embryos and eggs. This is because we were an early adopter of the technique of vitrification. Vitrification is an ultra-rapid freezing method that leads to much higher survival rates of eggs and embryos as compared to older slow-freezing methods. This technology has made it possible and realistic for women to electively freeze eggs before their age-related fertility declines to truly infertile levels.

Although we initiated our pilot project on freezing of donor eggs in 2006, we did not promote elective egg freezing until about 2011. The technology was still considered experimental and much more experience was needed to know this would be a safe and viable technology. Our pilot program did do well, however, and several healthy babies were born through this limited project. Subsequent to that, both the European Society for Human Reproduction and Embryology (ESHRE) and then the American Society for Reproductive Medicine (ASRM) have come out with position statements that egg freezing is no longer considered purely experimental. This is in light of the number of healthy babies that have been born world-wide after egg freezing. Cautions remain in place regarding elective egg freezing as the social implications still are to be seen and studied. However, for women bumping up against that biologic clock, this alternative to single parenthood using donor sperm is an attractive one and we are seeing ever-increasing numbers of women consulting with us in order to undergo IVF for the purposes of elective egg freezing.

I recently asked our embryology staff to provide a synopsis of the number of egg freezing cases we have done since Jan 2012 and here are the data through April 2013: At PFC, we have done 121 egg retrieval for egg freezing procedures. The average age of patients that have undergone egg freezing was 37.9 years (range: 28-44). The median age was 37. We have vitrified a total of 1443 eggs from these patients for an average of 11.9 eggs per patient per cycle. The age breakdown of these cases is given in this table:

What we do not yet have is data on the outcomes of thawing from fertility preservation patients as virtually none of these patients have yet come back to thaw their eggs. We do know, from our ongoing frozen donor egg bank, that rates of survival, fertilization, embryo formation and pregnancy are running comparably to fresh donor egg cycles and this gives us confidence that the eggs from these patients will do reasonably well when thawed.

One excellent question most patients ask is, how many eggs should I freeze? Based on fresh implantation rates, our best estimates are as follows:

• 12 eggs, if younger than age 37
• 12-20 eggs, if age 37-39
• More than 20 eggs, if 40 and older

These estimates are based on the probabilities of having 2-4 good embryos after thawing, fertilization and embryo growth and taking into consideration age-related implantation and pregnancy rates. So for many patients, it may be prudent to plan on banking eggs in 2 or more cycles of IVF stimulation.

There is no doubt that this is an exciting time in the field of assisted reproduction. For better or worse, it is a fact that women are getting married later in life and having their first child later as a consequence. Age-related sub-fertility is one of the most common diagnoses we see in our infertility patients. Giving young women this option of freezing of eggs before they are all gone or at least no longer viable is a remarkable process which we do not take lightly. We encourage our referring colleagues to discuss this option with their patients that are single and want a family in the future. We encourage the discussion and on-going debate about this technology. Now that egg freezing is going global, like it or not, it is here and it is likely not going away.

- Carolyn Givens, M.D.

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