Researchers at Children's Hospital of Philadelphia have developed an artificial womb in the hope that one day their device could be used to benefit babies born ahead of term.
The new invention, so far tested on eight fetal lambs, was designed to mimic the uterus of a pregnant animal and enabled very premature fetuses to develop normally for about a month.
"We've been extremely successful in replacing the conditions in the womb in our lamb model," said lead study author Alan Flake, who added the animals exhibited normal growth, brain, and lung development.
His team is the first to ever achieve this in extra-uterine conditions. At the beginning of their experiment, the tiny lambs were at the biological equivalent of premature babies in the 23 to 24 week gestation stage.
According to Flake, the artificial womb could be tested on very premature human infants in the next three to five years.
Womb In A Bag
The average gestation time for humans is 40 weeks, yet every year in the United States, approximately 30,000 babies are born ahead of 26 weeks.
Even younger infants coming into the world in the 22- to 23-week gestation stage typically weigh only about a pound and have less than a 50 percent chance of survival.
Of those who survive, many have severe disabilities, including lung disease and cerebral palsy. In the United States, extreme prematurity accounts for over one-third of all infant deaths and half of cerebral palsy cases.
"Extreme prematurity is the leading cause of neonatal mortality and morbidity," the authors wrote in their paper's abstract, published April 25 in the journal Nature Communications.
If the new device is successful in human trials, parents of babies delivered in preterm births might someday rely on an incubator that looks a bit like an aquarium.
The device is essentially a clear plastic bag filled with a liquid that mimics the amniotic fluid, which normally surrounds fetuses in the womb.
How The Artificial Womb Works
The new device evolved over a period of three years and has gone through a series of four prototypes.
The latest prototype was tested on five lambs that were surgically removed from their mothers after 105 to 108 days of gestation, when they were similar in development to a 23-week-old human fetus. The team also tested three lambs that were 115 to 120 days old.
One of the invention's key features that the premature lambs brought to term with this machine didn't breathe in air. Instead, they were suspended in the liquid inside the plastic bag.
Another important characteristic of the artificial womb is that it has no external pump to support blood circulation, a major improvement over the incubators and ventilators now used to keep preemies alive.
This is because even gentle pumps produce pressure that can fatally overload an underdeveloped heart, the researchers explain.
Instead, blood is pumped by the heart via the umbilical cord into a machine placed outside the artificial womb and acts as a substitute for the placenta. This feeds the fetus's bloodstream with oxygen and nutrients, doubling as a system for carbon dioxide removal.
"The whole idea is to support normal development; to re-create everything that the mother does in every way that we can to support normal fetal development and maturation," Flake underlined.
How Did The Lambs Fare In The Experiment?
The new device helped even the youngest lambs develop normally. The fetuses were able to move, open their eyes, and even grow wool while inside the artificial womb.
"Fetal lambs that are developmentally equivalent to the extreme premature human infant can be physiologically supported in this extra-uterine device for up to four weeks," the researchers state.
The authors go on to show "lambs on support maintain stable haemodynamics, have normal blood gas and oxygenation parameters and maintain patency of the fetal circulation."
As soon as they matured enough for their lungs and other systems to be sufficiently strong, the lambs were "delivered" from their bags and put on ventilators, where they showed normal lung function.
Despite many of the lambs being euthanized for the purpose of the experiment so that researchers could study their biology, there are two reported survivors.
One of them is now about four months old, while the other has already celebrated its first birthday. According to the researchers, both lambs were retired to a farm in Pennsylvania.
"They're reasonably normal in every respect we can tell," said Flake, adding the team plans to observe the survivors long-term to investigate any potential hidden morbidity.
The scientist pointed out the device is not meant to extend viability outside of the womb further back than 23 weeks. Equally, the new invention was not created with the purpose of bringing a baby to full term.
Rather, it is intended to function as a bridge between the mother's womb and the outside world, supporting the infant from 23 weeks to 28 weeks of gestational age, after which time the effects of prematurity are minimal.
"If you can just use this device as a bridge for the fetus then you can have a dramatic impact on the outcomes of extremely premature infants," noted Flake.