How Long Do Frozen Embryos Last? “Indefinitely” — But It’s Complex

You may have seen the news that, in October, a couple in Oregon welcomed twins from 30-year-old frozen embryos that had been donated to them. Amazing fact: The dad of the twins was only five years old himself when the embryos were frozen. Many experts believe they were the longest-frozen embryos to result in live births, though there have been other births from embryos over 20 years old.

It's enough to make anyone wonder: How long can frozen embryos last?

IVF is still new in the scheme of things.

Louise Joy Brown was dubbed the first "test-tube baby" when she was born in England in 1978 with the help of in vitro fertilization (IVF). She was implanted in her mom's uterus at day two. It was six years later, in Australia in 1984, when a baby girl named Zoe was born from a frozen embryo. Zoe's embryo had been frozen for eight weeks before implantation.

So, doctors and specialists have only been using frozen embryos for IVF for a little more than 35 years. It's been about 30 years since enough couples turned to IVF that a number of embryos went into storage. Frozen 30-year-old embryos are likely about the oldest there are, and there's no such thing, yet, as a 40-year-old frozen embryo to try.

In theory? Embryos can't go "bad."

I turned to a fertility specialist with 18 years of experience, Nora Miller, MD, of Greenwich Fertility (part of Yale Medicine), for an explainer of the freezing process. "We don't really know exactly how long embryos are viable. They're frozen in -80 Celsius — they're in liquid nitrogen," Dr. Miller says. "So, in theory, if the conditions are maintained, embryos can stay frozen indefinitely."

There's more to it, though. Dr. Miller says that, in those early IVF days, embryos like the one used for Zoe were only grown to day two or three before being frozen. When thawed, many of those embryos prove not to be viable.

Embryos are now grown to day five, six, or seven because "even in our youngest patients, up to half of those embryos will be genetically abnormal and stop growing," Miller says. This is to say that in the batches of the oldest frozen embryos, quite a few of them can't result in a viable pregnancy. Today, couples freeze healthier embryos — and fewer of them.

There are not a lot of frozen embryos sitting around.

If you Google it, the web will tell you there are either a couple hundred thousand or up to a million frozen embryos stored in the United States. But the truth is, no one has ever done a count; they've just guessed. The count would change every single day anyway, and those in the industry would caution that not all embryos could result in a viable pregnancy.

I have never had personal experience with IVF, so there's plenty I don't know. For instance, I should have realized this: Couples have to pay to store their frozen embryos, between roughly $400 and $1,000 a year. It's remarkable to me that any couple pays that for a few decades, hoping another couple will accept them for IVF. "Some people, especially those that are religious, feel very uncomfortable with the idea of discarding any embryos," Miller explains.

But that's a small subset of the parents that she sees. "Most people don't keep their embryos frozen. So, let's just say you finished [building] your family. You're very happy with your three kids — you're ready to move on. If you had extra embryos, most people are not donating them for adoption. They're uncomfortable with that option. Some people discard, and a very small percentage of people donate. And even with those donations, many of those embryos never make pregnancies," says Miller.

It's still most common for IVF patients to want to use their own egg and sperm, so the market for donated embryos is not huge. Though the answer to the question of how long embryos can last is that they can stay frozen for your lifetime (or as long as someone is paying to store them), the decision on how long to let them remain in a deep freeze is the final tough call for each set of IVF parents.