How long can human embryos stay frozen?

Through a process called cryopreservation, embryos — a group of cells that mark the earliest stage of human development — are frozen and stored in liquid nitrogen at minus 320 degrees Fahrenheit (minus 196 degrees Celsius), a temperature that stops all biological activity, Behr said.

According to a recent report, a healthy baby girl, named Molly Everette Gibson, was born from an embryo that had been frozen i.e, in 1992 and stored in a cryogenic (ultra-cold) freezer.
So how long can human embryos stay frozen before being implanted in a womb? Indefinitely, said Barry Behr, a professor of obstetrics and gynecology at Stanford University Medical Center.

Through a process called cryopreservation, embryos — a group of cells that mark the earliest stage of human development — are frozen and stored in liquid nitrogen at minus 320 degrees Fahrenheit (minus 196 degrees Celsius), a temperature that stops all biological activity, Behr said.

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Even if an embryo is put on pause for decades, once it’s thawed and implanted, it will continue to grow naturally. While there’s no limit to how long you can freeze an embryo biologically, there are outside factors that can damage the embryo.

Ionizing radiation from the sun puts some sort of limit on the indefinite lifespan of the frozen embryo because it can cause little mutations or damage to the cells’ DNA, Behr said.
The radiation can penetrate through any material except for lead — even the giant stainless steel or aluminum thermoses where frozen embryos are kept. But experts have hypothesized that it would still take up to a couple of hundred years, or a couple of lifetimes, for this radiation to affect the viability of the embryo.

The field of embryology and freezing methods have both greatly advanced since the time when experts first started freezing embryos in the 1980s.

Embryos used to be frozen using a slow-freezing method, and are now frozen with a very fast-freezing technique called vitrification. Also in the early days, embryos were frozen when they were made up of two cells or six to eight cells, now they’re frozen when they have around a hundred cells.

Evidence hasn’t shown any health differences in babies that were born from frozen embryos when compared with babies born from fresh embryo transfers, say doctors.
Eggs can be similarly preserved indefinitely.

 

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