According to a new study, frozen embryos have a better chance of yielding healthy babies than do fresh fertilized eggs.
It’s the stuff of science fiction — freezing living beings and then bringing them back to life sometime in the future. But in fact, reports abound of revivification occurring after freezing: Frozen lobsters have come back from the dead. A mouse was cloned 16 years after its demise. Frozen frogs have hopped again. Bacteria frozen during the Ice Age have been revived. And every day in the developed world, fertility clinics implant embryos that were frozen for years into women who want to conceive. Now amazingly, new research shows that those frozen embryos yield healthier babies than fresh ones do. (Think about that the next time you buy a dozen “fresh” chicken eggs.)
Frozen embryos are a byproduct of in-vitro fertilization (IVF) — a process of implanting fertilized eggs into women who have trouble getting pregnant via the usual route. In fact, about one percent of babies born in developed countries come from IVF. The usual process involves administering hormones to stimulate the mother’s uterus so that she produces an abundance of eggs, then harvesting those eggs and fertilizing them in a test tube by adding sperm, and finally transplanting a few of the fertilized eggs into the womb several days later. Often, more eggs get fertilized than can be used, and so the “leftovers” get frozen. If all goes well — voila — nine months later (give or take), an offspring is born and the frozen embryos are never used.
It’s a costly process not usually covered by health insurance, and certainly not fail-proof in spite of the $15,000 or higher price tag, per attempt. About half the time, the fertilized eggs don’t “take” in the womb, so the woman has to go for additional rounds, each time using some of those frozen “extras” from the original harvest, which are defrosted and implanted. Those eggs can remain viable in the freezer for 10 years or longer, though they usually get used within five.
Illogical though it first seems, the frozen embryos have a better chance of yielding healthy babies than do the fertilized eggs fresh out of Mama’s womb. In fact, a new study out of Finland found that babies born from frozen embryos were 35 percent less likely to be premature and a whopping 64 percent less likely to have low birth weight than babies born from fresh embryos. Meanwhile, research out of the University of Pennsylvania found that babies born from fresh embryos stand a 51 percent greater chance of having low birth weight, and a 15 percent greater chance of dying at birth.
These are significant numbers and would create a clear-cut argument in favor of freezing all IVF embryos — except that according to Dr. Allan Pacey of the British Fertility Society, “Frozen embryo transfers are not as successful as fresh ones in terms of getting a pregnancy.”
Nevertheless, it rubs against logic that an embryo that’s been frozen at minus 196 Celsius (minus 321 Fahrenheit) for five years should produce a healthier baby than the one fresh out of the test tube, but experts have put forth some theories as to why. One possible explanation is that women who were healthy enough to produce extra eggs to freeze would naturally have healthier offspring than women who only produced enough eggs for one “fresh” attempt. Another theory is that only the hardiest embryos can survive the freezing process. And a third theory suggests that since fresh embryos get implanted only a few days after a woman takes the ovary-stimulating hormones, the drugs are still circulating in her system and can damage the fetus.
While it’s intriguing to discover that frozen fetuses outperform the fresh ones, it’s probably not an issue of concern for the average woman who has paid the price tag for IVF. Experts agree that since fresh embryos offer better odds of conception, they’re still the first choice in spite of the risks. But what is an issue for women attempting to conceive via IVF is the problem of what to do with the extra frozen fetuses that aren’t needed, especially now that it’s clear that, in fact, those fetuses likely will yield healthier babies.
Once a woman conceives, if she doesn’t want more kids, she can either throw out the frozen embryos, donate them for research, give them to another hopeful parent, or keep them frozen indefinitely, paying an annual storage fee. A recent New York Times article says that in the US alone, there are currently an astounding 400,000 frozen embryos with undecided fates, with more added every day. Apparently, regulations have made it increasingly difficult to donate the eggs to other couples, and more than half of those parents with frozen embryos don’t want to donate them anyway. Forty-three percent don’t want to throw the extras away, and 44 percent don’t want them used for research. And so, increasing numbers of people are opting to keep those fetuses frozen indefinitely.
(As a side note, embryos aren’t the only thing improved by freezing.)