On October 26, 2020, a healthy baby was born from a fetus that was frozen for 27 years, a record for the longest human fetus that remained frozen before its birth, according to recent news reports.
Molly Everett Gibson was born from an embryo that was frozen in 1992 and stored in a very cold freezer, according to the Washington Post.
Molly's trip broke the record set by her older biological sister, Emma Wren Gibson, whose unborn baby had been frozen for 24 years before she was born. Given this news, questions began to arise about how many years could embryos remain frozen.
"Indefinitely," said Barry Bearer, professor of obstetrics and gynecology at LU Medical Center.
Through a process called cryopreservation, embryos, a group of cells that represent the first stage of human development, are frozen and stored in liquid nitrogen at minus 320 degrees Fahrenheit (-196 degrees Celsius), which is the temperature that stops all biological activity. As Bear said.
"If all biological activities stop, then basically you press the pause button and things resume when the pause button is turned off," he added.
Even if the embryo is stopped for decades, once it is thawed and implanted, it will continue to grow normally.
Beer explained that while there is no limit to how long you can biologically immobilize an embryo, there are external factors that can harm the fetus.
He said ionizing radiation from the sun "sets a kind of limit to the indefinite life" of a frozen embryo because it can cause minor mutations or damage to the DNA of cells.
And radiation can penetrate any material except for lead, even giant stainless steel or an aluminum thermos where frozen embryos are kept.
But experts assumed it would take up to a few hundred years, or a few periods of life, for this radiation to "significantly" affect the viability of the fetus.
Dr. Mary Ellen Pavon, associate professor of obstetrics and gynecology at Northwestern Medicine in Illinois, agrees with Dr. Bear that by using modern methods of freezing, embryos can be "largely stored indefinitely".
She said that initially the embryos were frozen using the slow freezing method, and are now being frozen using a very fast freezing technique called "vitrification".
Moreover, embryos are now frozen at a later stage of development, when they are more robust. Pavon pointed out that in the early days, embryos were frozen when they were only two or six to eight cells, and now they are frozen when they have more than a thousand cells.
Bear said that the evidence did not show any health differences in children born from frozen embryos compared to children born from new embryos, explaining that there are slight differences reported in the scientific literature between the two, but these differences are in the endometrium, or mucous membrane of the mother's uterus. Surrogate, not the fetus.
And Dr. Pavon noted that the vast majority of embryos implanted that do not lead to pregnancy have essential abnormalities, which were not caused by the freezing process. But if an embryo that has been frozen for centuries has achieved pregnancy, "there is really nothing to indicate that the pregnancy will change because of the length of time the embryo is frozen for," she said.
Source: LiveScience
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