In May, for the first time, Fertility and Sterility published research data from a New York Medical College and the University of California Davis meta-analysis on egg freezing cycles. The researchers used patient data from January 1996 to July 2011 to report the probability of live-births from IVF cycles with ICSI using eggs frozen by both the slow freeze and vitrification methods. Eligibility qualifications, to ensure apples to apples comparisons, stipulated that no mixed cycles (i.e.: slow freeze and vitrification, or fresh and frozen embryos) be included in the analysis.
Ultimately, the study yielded data on 2,265 cycles collected from 1,805 patients from 11,122 slow frozen eggs and 1,957 vitrified eggs. Women included in the research were between the ages of 20 and 51 at the time of freezing– with 34 being the average age. The slow freeze method yielded 253 pregnancies and 163 live births and the vitrified eggs resulted in 75 pregnancies and 61 live births (note: the low number of vitrified eggs included in study). As most of us are already painfully aware, live birth rates in this study, from both slow and vitrification methods, correlated tightly to patient age. However, …and here is the silver lining, live birth rates did occur with 42 year old eggs with the slow method and 44 year old eggs with vitrification.
Some other fun facts from the study:
– Survival & fertilization rates were higher with vitrified vs. slow frozen eggs
– 30 year old slow frozen eggs had a 8.9% likelihood of implantation success
– 40+ year old slow frozen eggs had a 4.3% likelihood of implantation success
– 30 year old vitrified eggs had a 13.2% likelihood of implantation success
– 40+ year old vitrified eggs had a 8.6% likelihood of implantation success
If you really want to roll your sleeves up and dig into the research, the detailed tables highlights the results of the study.
I must admit that initially I found these statistics a bit alarming. However, there are a few caveats to bear in mind: 1) The study was conducted over a 15 year period and egg freezing techniques are evolving rapidly. 2) The expertise of the lab and doctor is not taken into consideration. 3) The quality of thawed eggs and resulting embryos are not classified.
The overarching conclusion of the study hammers home one key theme: age matters. However, as a 39 year old egg freezer, I know what my chances of conception are with my frozen eggs and although they may not be great, I’d rather have those odds than none at all.