Dr. Jones: What do you call a human egg five days after fertilization that's in the freezer? This is Dr. Kirtly Jones from Obstetrics and Gynecology at 麻豆学生精品版, and this is The Scope.
Announcer: Covering all aspects of women's health, this is the Seven Domains of Women's Health with Dr. Kirtly Jones on The Scope.
Dr. Jones: This week in the news was a report of a live birth, of a baby resulting from an embryo, a zygote, preimplantation embryo that has maybe from 8 to 100 cells that was frozen 24 years ago. Reportedly, this is the longest time between freezing and live birth, at least that we know of, at least in the U.S. In reality, this record is going to be broken regularly as the technology which allowed us to freeze early preimplantation embryos became regularly used over 20 years ago. So more and more babies from embryos in long-term storage will be used. We'll be hearing about babies 30 years, 40 years, 50 years from conception and on and on.
Now, for just a little moment, let's step aside into comparative reproductive biology and talk about bears. Bears in winter. Bears and some 100 other animals do something called embryonic diapause. Cool name, huh? Well, I think it's cool. This is a natural process wherein a bear egg gets fertilized by a wandering bear sperm and progresses a few days and then stops growing, pauses through mechanisms we don't understand very well, for months. It just hangs out in the fallopian tube until a bear goes into hibernation, and then the preimplantation embryo implants and grows while a bear is hibernating. The goal is to postpone the birth until the appropriate environmental or metabolic conditions for the animal, in this case, the bear. The bear cubs aren't born until near spring when there will be an abundance of food. These pre-embryos in suspended animation are not frozen. They're in the mother but not growing until later.
By the way, to the best of our knowledge, humans can't really do embryonic diapause in the mother's body, but we can put our embryos in the freezer, probably indefinitely. In the in vitro fertilization world, usually a number of eggs are produced either by the biological mother or by an egg donor and then fertilized. In the U.S., we're trying to decrease the rate of risky twin, triplet, and quad births by putting back only one or two pre-embryos. In the U.S., we offer the chance to freeze the rest of preimplantation embryos, which for the sake of easier, we're just going to call embryos, but they only have about 8 to 100 cells.
Now, these aren't frozen in an ice cube tray in a regular fridge, but are very carefully frozen so as to not make ice crystals in the embryos and kept in liquid nitrogen. There are probably millions of cryo preserved embryos in the world with regulations about what can be done with them differing from country to country. For instance, currently, embryos cannot be frozen in Italy. In the U.S., there aren't really any rules and regulations except that IVF embryo labs must be certified. Being able to freeze unused embryos from an IVF cycle allows couples to have another chance of becoming pregnant or have another baby, or have a lot more babies if they want. But what happens if they don't want, couples who have the family size they want, who get divorced, or who get too old?
In the U.S., we offer couples three options. They can donate the embryos for research. They can thaw the embryos without transferring them to a uterus and the embryos will die, or they can be donated to an embryo bank that allows for embryo adoption. The case of the baby recently born from an embryo created 24 years ago arose from a couple that received the embryo from an anonymous donation to an embryo bank that specializes in embryo donation, the National Embryo Donation Center. This child born to an infertile couple who desperately wanted children is possibly the best outcome for unwanted embryos.
There are issues, however. The genetic parents are anonymous, so it'll be hard for the new parents and baby to know their genetic heritage. Of course, with more and more people choosing to search out their ancestry with genetic testing, children and adults from donor sperm, donor eggs, and donor embryos are finding genetically linked persons and figuring it out on their own. In Great Britain and Australia, there are laws which prohibit anonymous donation of eggs, sperms, and embryos, and the genetic parents must be on file for the child to know about when they turn 18.
In the U.S., advanced reproductive technology is less regulated than in Europe, so the origins of the frozen embryos, the so-called snow babies, can be anonymous. But between the donation of extra embryos from the couple 24 years ago and the so-called adoption of the embryos a year ago, when the embryos were in the bank, who owned them? Who was responsible for them? What was their legal status? Should they even have a legal status? If there are egg banks and sperm banks, what do we think about commercial enterprises that create embryos, you pick the color, ethnic background, whatever, of the genetic egg and sperm donors, and they will make embryos for you for sale? There's a little bit, actually a lot, of the yuck factor going on there for me.
In the end, it's probably a good thing that couples who have excess frozen embryos don't have to destroy them if they don't want to. And it's a good thing that they don't have to use them if they already have the family that they want and want no more children. That means there's a place for an embryo adoption center. It also means that couples who cannot make their own embryos for some reason but want to experience pregnancy and having a baby from birth can do so, but we're still left with some sticky issues like who's responsible for the embryos for quarter of a century, or half a century, or a century who have no legal parents, and what right does the grown person have to know who they are? So in this season of snow and miracle babies, thanks for joining us and the snow babies on The Scope.
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