It sounds like the plot of a bad sci-fi movie - human babies are removed from their mothers' wombs and grown in liquid-filled capsules.
However, this is exactly what scientists from the Children's Hospital of Philadelphia, in the US state of Pennsylvania, propose to do with babies who are at risk of being extremely premature.
They are developing a system they called an "artificial womb", more precisely an extrauterine environment for the development of a newborn, in English the abbreviation Extend (Extend) for extra-uterine environment for newborn development.
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Such an environment is not intended for the development of the fetus from conception to birth - it would be impossible even if it were desired.
The goal is to contribute to a higher survival rate of extremely premature babies who face many possible health consequences throughout their lives.
A typical healthy pregnancy lasts about 40 weeks, and the baby is considered ready to be born at 37 weeks.
However, sometimes complications occur during pregnancy that can lead to premature birth.
Fortunately, thanks to the huge advances in neonatal medicine over the last few decades, most premature babies survive with few complications.
The latest data show that as many as 30 percent of babies born in the 22nd week of pregnancy survive if they are given appropriate intensive care.
"Frankly speaking, babies born at 28 weeks and even 27 weeks of gestation generally do well," says Stephanie Kukora, a neonatologist at Children's Mercy Hospital in Kansas City.
"However, the outcomes for babies born between the 22nd and 23rd week of pregnancy are so severe that we are not sure if the quality of life they achieve is acceptable."
Babies born on the edge of survival often face serious health problems.
These babies weigh less than 900 grams at birth, and vital organs such as the heart, lungs, digestive organs, and brain are not yet developed enough to keep the baby alive without intensive medical care.
Among the frequent short-term complications are necrotizing enterocolitis, a serious disease of inflammation of the intestinal lining that causes it to begin to die.
Children of this age are very prone to infections, sepsis and septic shock - a life-threatening drop in blood pressure that can damage the lungs, kidneys, liver, and other organs.
Long-term consequences that can occur in extreme prematurity include cerebral palsy, moderate to severe learning disabilities, vision and hearing problems, and asthma.
Even the very technology designed to save babies' lives—oxygen therapy and mechanical ventilation—can harm a baby's fragile lungs.
"At that early stage of pregnancy, the lungs are still developing and should be filled with fluid," says George Mikaliska, professor of surgery and obstetrics at the Children's Hospital of the University of Michigan.
"But when they're born extremely premature, we do endotracheal intubation and put high-flow, high-pressure air and oxygen into their lungs — and that's been documented to cause lung injury."
Over time, these injuries scar the lungs and cause a condition known as bronchopulmonary dysplasia, or chronic lung disease.
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Children are often discharged from the hospital in a condition that requires long-term oxygen therapy and mechanical ventilation for the rest of their lives.
Mechanical ventilation can also increase the risk of retinal damage.
The blood vessels that feed the retina of the eye are not fully formed until birth.
Too much oxygen can cause new, abnormal blood vessels to grow, which can eventually lead to retinal detachment.
The goal of creating an artificial uterus and placenta is not to touch the lungs, but to allow the fetus time to continue developing in a safe environment until the baby is ready to take its first breath.
There are three main groups working on the development of this technology.
All three groups rely on an existing therapy called extracorporeal membrane oxygenation (ECMO), also known as an artificial lung, which helps a person whose lungs and heart are not working properly.
With this technique, blood is pumped from the patient's body into a machine that removes carbon dioxide and adds oxygen.
The oxygen-rich blood is then returned to the patient's circulation.
With this method, the blood "bypasses" the heart and lungs, which allows these organs to rest and heal.
Although Ecmo can be used in older babies, it is not suitable for extremely premature babies.
All three teams try to make the smallest possible version of the system and adapt the technology.
However, there are subtle differences between the devices being developed.
Scientists at the Children's Hospital of Philadelphia, led by fetal surgery specialist Alan Flake, plan to immerse premature babies in liquid-filled capsules designed to mimic the amniotic fluid (amniotic fluid) of the womb.
Surgeons would then connect the small blood vessels of the baby's umbilical cord to a device similar to the Ecma.
Blood pumps the heart of the fetus, just like in the natural environment.
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In 2017, Flake and his colleagues took eight premature lambs at a developmental time equivalent to a human fetus of 23 to 24 weeks' gestation and kept them alive in an artificial womb for four weeks.
During that time, it seemed that the lambs were developing normally, even their fleece was growing.
George Mikaliska's team at the University of Michigan is developing something they call an artificial placenta.
Instead of submerging the entire fetus in the liquid, they plan to use breathing tubes to fill the newborn's lungs with a specially developed liquid.
Their system drains blood from the heart via the jugular vein, similar to traditional Ecmo machines, but returns oxygen-rich blood via the umbilical vein.
"I wanted a method that was easily accessible to most babies and could be used in existing neonatal intensive care units," says Dr. Mikaliska.
"Technology is not intended to replace the placenta's myriad functions.
"It is focused on gas exchange and maintaining the blood pressure, heart rate and circulation of the fetus while the still unformed organs are protected and continue to develop".
During a recent artificial placenta trial, premature lambs survived 16 days using the machine before being safely transferred to mechanical ventilation.
During this period, their lungs, brain and other organs continued to develop well.
A third group, a team from Australia and Japan, is developing an artificial womb called Eve Extrauterine Environment Therapy (ex vivo uterine environment).
Compared to the other two methods, this one is more dedicated to creating a system that can be applied to more premature babies and sick fetuses.
"We can now take a 500-gram fetus [lamb] and maintain it for two weeks in what I would describe as a normal physiological state," says Matt Kemp, professor of obstetrics and gynecology at the National University of Singapore, who leads the Eve project.
"It's a pretty great achievement, but on the other hand, the growth of these fetuses is abnormal."
Most trials using artificial placentas/wombs have been conducted on lamb fetuses that are otherwise healthy and would have survived to term had they not been deliberately removed.
The problem is that extreme premature babies are often born prematurely due to health complications of the mother or the fetus itself.
This makes them more difficult to treat.
"In an experiment we performed on fetuses whose health was quite impaired, we saw that it was much more difficult to keep those animals alive," Kemp emphasizes.
"They develop much worse and it is much more difficult to maintain their normal blood pressure and circulation.
"So that's the situation - yes, we're making good progress, but there are still a lot of things we need to solve."
When will artificial placentas and wombs be available in hospitals?
The Children's Hospital of Philadelphia has probably gone the furthest in developing their solution.
The team recently applied to the US Food and Drug Administration (FDA) for permission to begin human trials of Eksten.
Mikaliska, whose team has further reduced the size of the system it is developing to fit the tiny blood vessels of a newborn, hopes to begin clinical trials in humans in about three or four years.
However, Kemp believes there are still many fundamental unknowns about how a fetus grows in an artificial womb and that knowledge must be complete before human trials can begin.
"We think it's pretty clear that a very small fetus doesn't have the ability to direct its own growth in a normal way, and that gets worse when it has some additional problem," Kemp explains.
"So we're trying to find out what the role of the placenta is in initiating these normal growth processes.
"We have almost reached that point. It is, to put it mildly, quite a big task".
There are also ethical issues.
In a recently published article, Stefani Kukor argues that there are subtle differences between the methods being developed and that there are ethical issues related to each.
For example, the artificial wombs developed by the Eve Project and the Children's Hospital of Philadelphia require the placement of a cannula on the umbilical cord, which means that the baby, immediately after being removed from the mother's stomach, must be attached to the device because the umbilical artery closes quickly after birth.
This means that mothers who could otherwise give birth vaginally would have to undergo a caesarean section in early pregnancy.
"When a caesarean section is performed so early in pregnancy, it cannot be performed the way it is done when it is time to give birth," explains Kukora.
"Such a procedure involves an incision that passes through the muscular layer of the uterus, and this can affect future pregnancies - whether the mother will be able to carry the future pregnancy and whether she will be able to give birth vaginally."
There are more risks associated with this procedure compared to vaginal birth, which is why the issue of informed parental consent also arises.
"I think one of the biggest issues is how we approach prospective parents about this trial," says Kukora.
"You can imagine the parents who are dealing with this really sad situation, who have just received news of bad outcomes at 22 weeks pregnant and who would be overjoyed at something new, even if it's not tested.
"Parents will do anything for their baby".
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Another problem with the procedure of immediately switching the baby to the Extend system is that there is no possibility to assess how the baby would respond to conventional therapy.
"There's not a lot of data beyond the week of pregnancy to make a decision about which baby needs to be put on the Extend system — because the baby isn't born yet, so you don't know how far along it is," says Dr. Mikaliski.
This may mean that babies who would otherwise respond well to traditional therapy could be treated with new, unproven technology, the risks of which are much less quantified.
However, Dr. Mikaliski believes that the Extend system would be beneficial for most babies born between 22 and 23 weeks of pregnancy, which are known to have a high rate of mortality and morbidity.
Because it drains blood from the jugular vein rather than the umbilical artery, doctors have more time to place babies in the artificial placenta Dr. Mikaliski is developing.
This allows doctors to assess the risks that babies face at birth and thus refer only the sickest babies to clinical trials.
Also, newborns could be treated with conventional therapies, before being transferred to an artificial placenta in case they are not developing properly.
Unlike the other two techniques, mothers can also give birth vaginally.
Whichever of the developing systems begins clinical trials first, the first patients are likely to be babies born before the 24th week of pregnancy who have very little chance of surviving with a good outcome with conventional treatment.
"I think that thanks to technology, the treatment of premature babies will progress, and that the artificial placenta and the Extend system will be applied in clinical practice," says Dr. Mikaliski.
"But it also carries potential risks that should be assessed in the initial stages of safety testing."
"I think that initially this technology should be applied to babies who have little chance of survival, and when we determine the risks and effectiveness of this technology, it should be applied to other premature babies as well."
If successful, all three technologies will provide much-needed hope to parents who unexpectedly have a premature baby.
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