Equipment failure is being blamed for the loss of thousands of frozen eggs and embryos at a medical facility in Cleveland last week. At least 2,100 frozen specimens were said to be lost when the cryogenic tank their were stored in became too warm.
Success rates for egg freezing, which has been around since the 1980s, have risen with a newer process that “flash freezes” the eggs, called vitrification. In 2012, the American Society for Reproductive Medicine declared egg freezing was no longer experimental.
But a rise in temperature in the storing facility can be disastrous. To learn more about the process and what can happen if specimens don’t stay frozen, we spoke with Staci Pollack, MD, Ob/Gyn, Division of Reproductive Endocrinology & Infertility and associate professor, Reproductive Endocrinology & Infertility, Department of Obstetrics & Gynecology and Women’s Health, Montefiore Health System and Albert Einstein College of Medicine in New York.
Here is an edited version of our conversation.
WebMD: What happens to embryos or eggs when they become too warm?
Pollack: Eggs are frozen with nitrogen. And when they warm up, the embryo is either going to survive or it’s, unfortunately, not going to survive, it’s going to die. It’s really an all or nothing phenomenon.
WebMD: News reports on the Cleveland situation says the only way to know if they’re still viable is to thaw them and implant them. Is that your understanding of the process?
Pollack: Once we thaw an embryo or egg we can pretty much tell when it’s thawed before we put it back in whether it’s viable. If you mean that it’s still alive, you can tell that when you thaw it. What intended parents really want to know if it will make a baby, and in that case you won’t know for 9 months later and you have a baby in your arms. There are, of course steps, along the way. Did you get actually pregnant, is the pregnancy going smoothly.
Whether we’re using eggs or embryos that are fresh or frozen we don’t know that until you have that baby.
The answer would be, in terms if there was a tank mishap, you would know right away once you thaw if it’s viable.
WebMD: If specimens thaw for whatever reason, can you refreeze them?
Pollack: This is quite unusual. In terms can we properly thaw an embryo and refreeze it, the answer is you can, but viability goes down. Every time we stress that egg or embryo, every time we freeze and thaw we stress those eggs and embryos. We don’t really routinely freeze and thaw eggs and embryos.
WebMD: What should people who have eggs or embryos stored somewhere do? Go to the clinic and make sure they’re specimens are protected properly?
Pollack: Labs end up getting accreditation through the reproductive accreditation program (known as CAP accreditation, for College of American Pathologists), they get a CAP certificate that lasts for 2 years. If a lab is CAP accredited there are certain processes and protocols that they’ve been scrutinized for.
CAP is an accreditation program along with standards from the American society of Reproductive Medicine. These are specific for reproductive labs. If the lab is CAP certified they have standards by which you need change your tanks and have a process for checking them. At our center we refill our tanks (with liquid nitrogen) every week and we check them twice a week.
Patients can certainly ask if your lab is CAP certified and how often do you check your tanks.
WebMD: What else should we have asked but didn’t?
Pollack: It’s reassuring for patients to know this is an anomaly. We don’t know about it happening often. It is scary. If we can ever find a silver cloud in such event we can say hopefully this will lead people to make even greater protocols for the safety of their future babies.