You may have recently seen our announcement of the first baby born from a frozen donor egg in Texas. We are so happy and proud to have been able to bring this new technology to Texas and we look forward to using it to help many more of our patients in the near future. Unless you follow this field closely, you may be wondering what the big deal is, since we have been freezing sperm and embryos and using donor eggs and sperm for years. In fact, this latest accomplishment is significant for many reasons.
While it’s true that we have been freezing both sperm and embryos for decades, eggs have been extraordinarily difficult to freeze successfully.
There are many reasons for this, not the least of which is that the egg is the most complex cell in the human body. When we get a sperm specimen for freezing, it may contain 50-100 million sperm. When we freeze and then thaw the specimen, only 50-60% of those sperm may survive. That leaves us with plenty of viable sperm to use. Similarly, when we freeze embryos that have at least 8 cells, 80+ or more will survive the process (ie. at least one cell of the original 8 will survive intact – enough to make a completely normal baby). When we freeze an egg, on the other hand, there is only 1 cell to begin with. If that cell fails to survive, it’s all over.
So how do we freeze and why don’t cells always survive?
In fact, “freezing” of eggs is really “freeze drying”. The egg, the largest cell in the body, is composed mainly of water. If we simply freeze the egg, the water can form ice crystals, which can damage the chromosomes (DNA) inside and ruin the egg. Therefore, rather than freeze the egg, we have to first remove the water. We then replace the water with a non-toxic “antifreeze” that allows the other structures inside the egg to survive being frozen at 400 degrees below zero for a long time.
The technology that we used in the past to accomplish egg freezing involved putting the egg in a medical-grade plastic vial and slowly dropping the temperature using a programmable freezing machine. Once the egg reached a specific temperature, we would drop the vial into liquid nitrogen in order to rapidly complete the freezing process. Using this technology, about half of the eggs would survive, and programs around the world reported pregnancy rates of 2-3% per egg. Therefore, one could expect a 40% or so pregnancy rate if we could freeze 20 eggs – something that very rarely happened, as only our youngest patients even produce that many eggs.
Our new technology, developed in conjunction with good friends in Atlanta, uses a different type of non-toxic “antifreeze” and other equipment that allows us to rapidly freeze the eggs. They have been using this technology for several years now, and have reported 50-55% pregnancy rates with the use of 6 or fewer eggs.
Worldwide, there have now been several hundred babies born from egg freezing technology. Although the technology is obviously too new to definitively declare it to be free of long term side effects, so far no adverse effects have been reported.
So why is this new egg freezing technology such a big deal? In fact, there are many types of patients who can benefit from this new technology. Cancer patients can have their eggs successfully frozen prior to undergoing chemotherapy, radiation, or surgery. Women who want to electively preserve their fertility can now take advantage of this new technology to give them some degree of comfort that they will be able to conceive at an older age.
In addition, for the past 10 years or so, we have been prohibited from using fresh donor sperm for insemination – due to the risk of transmission of such diseases as HIV, Hepatitis B, Hepatitis C, and syphilis, among others. Sperm donors undergo testing for these potentially infectious diseases; they then produce sperm specimens which are frozen for a minimum of six months, and then they are retested to ensure that they are still disease free. Unfortunately, as we have not been able to successfully freeze eggs, couples who used donor eggs have had to risk acquiring these diseases as a result of using fresh eggs. Now, as a result of this new technology, couples using donor eggs can have the choice of using frozen donor eggs that have been quarantined and are, therefore, disease free.
As most successful IVF programs report pregnancy rates from fresh donor eggs in the range of 50% or so, there is no “fall off” in the chance for success by using frozen donor eggs. On the other hand, the most successful IVF programs, such as ours, have reported donor egg pregnancy rates of 70% or so per cycle, so there would be a slight decrease in the chance for pregnancy. The good news is that couples at TFC who desire donor eggs now have a choice.
Is this technology available everywhere? In fact, many IVF programs say that they can freeze eggs. The overwhelming majority, however, have never reported a successful birth once the eggs have been thawed and used. The key question to ask is not can they freeze eggs, but have they produced a successful pregnancy.
We believe, as a result of reported successes like ours, that the FDA will soon require IVF programs to use only frozen donor eggs. We are so happy that this technology will allow TFC to remain on the forefront of fertility treatment and we will continue to strive to develop more technologies to make fertility treatment even more successful and safe for our patients.