In a sterile, brightly lit lab, a tiny hairless creature lies perfectly still. It’s not even breathing — though thanks to tubing in its jugular and navel, it’s getting in oxygen and expelling carbon dioxide, and is 100 percent alive. At this point, the little lamb should still be floating around in its mother’s amniotic sac. Instead?
She’s hooked up to an artificial placenta.
Over the last decade, several dozen premature lambs have been incubated in external wombs — devices that aim to buy preemies some extra time for lung development. Researchers believe that the technology could help the tiniest of human preemies — the so-called ELGANs, or extremely low gestational age newborns, born before 24 weeks. Some 40,000 to 50,000 are born each year in the U.S.; their odds of survival are a meager 50 percent, and the risk of brain damage and other crippling health problems are high. Mechanical wombs could boost those odds and make even earlier births viable. The new technology also could have a major impact on a perennial hot-button issue — abortion — by upending careful legal compromises around fetal viability.
Researchers at the University of Michigan and the University of Pennsylvania, as well as in Japan and Australia, are trying to mimic the uterine environment by circulating oxygen and removing carbon dioxide through the blood instead of the lungs, which start out as fluid-filled sacs. Recently, scientists have crossed an important threshold by publishing their findings in scientific journals, offering evidence that artificial placentas can extend life by weeks — at least when it comes to lambs. According to Dr. George Mychaliska, a fetal surgeon and the lead researcher of the Michigan studies, the technology could be tested on human babies within five years. “It’s a huge team effort,” Mychaliska says, and one that earned his group $ 2.7 million in funding from the National Institutes of Health.
The lungs are an ultrapreemie’s most vulnerable organ. The ventilators currently used present a horrible Catch-22: They keep the infants alive, but destroy their delicate lungs in the process. Hence the race to perfect an artificial placenta that can help ELGANs reach week 26 or 27, at which point their lungs are strong enough to handle ventilators. The technology relies on extracorporeal membrane oxygenation, or ECMO, without relying on the heart/lung bypass machine ECMO usually utilizes. It’s no coincidence that Dr. Robert Bartlett, who invented ECMO in the late 1970s, is Mychaliska’s mentor and collaborator on the Michigan artificial placenta research.
If an artificial womb sounds like something in a sci-fi movie, well, it is — the device originally featured underwater pods and looked “like The Matrix,” says Mychaliska. (These days, the placenta looks more like an incubator you’d find at any neonatal intensive care unit.) But for the parents of ultrapreemies, the technology could be a game changer. They are the ones, not doctors, who must make wrenching decisions about whether to pursue treatment for their ultrapreemies. Doctors provide parents with as much information as possible, while conceding that predicting outcomes is mostly guesswork. Whether to treat an ELGAN “may be the most difficult decision in medicine,” says George Annas, director of the Center for Health Law, Ethics & Human Rights at Boston University’s School of Public Health. The artificial placenta would postpone life-and-death decisions until a baby’s odds of surviving without chronic disability are higher.
But a few notes of caution before parents get their hopes up. Some experts note that decades of research have added only one week of viability for ELGANs, and they are skeptical about any protocol that promises radical improvements. Dr. Amen Ness, a maternal fetal specialist at Lucile Packard Children’s Hospital at Stanford University, says an artificial placenta could be a boon, but what doctors really need to figure out is how to prevent preterm labor in the first place. “We still don’t understand the big bang, the thing that doesn’t go right that causes [labor] to start,” Ness says. Figuring that out“would put us out of jobs” (and make artificial placentas obsolete too). Others question whether the success of an artificial placenta will translate from animals to humans. Many animal experiments fail when applied to studies with humans, says Alka Chandna, a laboratory oversight specialist at People for the Ethical Treatment of Animals. There are “striking differences” between lamb and human fetuses, Chandna says. Mychaliska counters that his team chose fetal lambs because their lung development closely mimics that of 24-week-old babies.
And then there’s something that even the most gung ho researchers would rather not discuss: Pushing back viability could raise big questions surrounding abortion laws. Rulings by the U.S. Supreme Court allow states to ban abortion at 24 weeks of gestation, when “catastrophically bad outcomes [shift] to a 50 percent chance of survival,” says David Magnus, director of the Stanford Center for Biomedical Ethics. That legally defined boundary was enough for 27 states to pass legislation that bans abortions after 24 weeks. If the 50 percent survival rate moved to, say, 23 or 22 weeks, bans might be pushed back as well. If Mychaliska and his team succeed, the impact of their studies with premature lambs could ripple across the country — and all the way to the Supreme Court.
