The researchers then attached the umbilical cord to a machine that exchanges carbon dioxide in blood with oxygen, like a placenta normally does.
Researchers are creating an artificial womb to improve care for extremely premature babies - and animal testing suggests the first-of-its-kind watery incubation so closely mimics mom that it just might work.
The trials, carried out by a research team at the Children's Hospital of Philadelphia, grew the lambs in a transparent pouch they called a Biobag, which allowed them to breathe lab-made amniotic fluid and continue to develop as they would in the womb.
The artificial womb study has been fast tracked by the US Food and Drug Administration and the researchers are now undertaking further animal trials, which they hope to complete within two years, "then move on to first in human use within three to four years", Dr Davey said.
According to Flake, his research team has already been in contact with the United States food and Drug Administration and trials of the device could start sometime in the next three to five years.
The CHOP researchers tested the device in premature lambs, and published the results of their research today in the journal Nature Communications. The lungs and brains of the lambs were uninjured and just as developed as those who grew in a regular womb. "They've had normal development in every way that we can measure it", Flake said.More news: Sharapova sails into Stuttgart semis
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In the future, these biobags may be used to help premature babies survive. "Infants that are now born and supported in a neonatal intensive care unit with gas-based ventilation demonstrate an arrest of lung development, which manifests in the long term with severe restriction of function, which can translate into lifelong morbidities", coauthor Emily Partridge told reporters.
Scientists believe it could be ready for human trials in three to five years.
In the study, the premature lambs, equivalent in age to 23to 24 week-old human infants, appeared to develop normally in their bags.
A lamb inside the artificial womb.
"So many research groups have been trying to develop a system like this since the 1950s, however they've met with limited success", Dr Davey said.
In a video that accompanied the release of the study, Emily Partridge, a research fellow at the hospital, described being struck by the sight of the zipped-up lamb fetuses, "breathing, swallowing, swimming, dreaming" - all with "complete detachment from the placenta and from mom". It could also reduce the estimated $43 billion hospitals spend on premature infant care annually.