In the system, which has only been tested in animals so far, the premature infant is placed in a plastic bag filled with a substitute for amniotic fluid.
In hopes of building a better incubator, the team at CHOP created multiple prototype devices, eventually creating a device that features a biobag filled with amniotic fluid and a machine to oxygenate the blood via the umbilical cord.
Scientists have been able to keep a baby sheep alive for weeks using an artificial womb that resembles a plastic bag. Doctors are also interested in adding some subtleties like audio recordings that simulate sounds a fetus would normally hear in the womb, like the mother's heartbeat.
In pre-clinical trials with lambs, experts were able to mimic the environment similar to the womb along with the functions of the placenta. The researchers say the system wouldn't change the limits of when a fetus can survive. Helping premature babies to survive is a growing challenge because advances mean more premature babies are surviving birth, but there still is the challenge of helping them survive and preventing illness, or morbidity.
The full details of the discovery were in Nature Communications.
Associate professor David Tingay, a neonatal researcher at Murdoch Childrens Research Institute, said people had been trying to create an artificial womb for more than 50 years and this model was the most promising yet. They also used three lambs that were slightly more mature, age 115 to 120 days.
"This unique womb-like, fluid environment could bridge the critical time from mother's womb to outside world and reduce mortality and disability for extremely premature infants", officials said in a statement on the CHOP website.
But Dr Flake said there was no technology "even on the horizon" that could replace a mother's womb at the earliest stages of foetal development.
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In this photo provided by the Childrens Hospital of Philadelphia, fetal physiologist Marcus G. Davey of the Childrens Hospital of Philadelphia, who helped design the artificial womb system.
The team will next work on refining the system and prepare it for human infant use.
"This will require a lot of additional preclinical research and development and this treatment will not enter the clinic any time soon", Colin Duncan of the University of Edinburgh, Scotland, who was not involved in the research told BBC News.
"Fluid is very important in terms of fetal lung development", said Flake.
"This system is potentially far superior to what hospitals can now do for a 23-week-old baby born at the cusp of viability", Flake said.
She noted that human testing is still three to five years away, although the researchers are already in discussions with the Food and Drug Administration.
He acknowledged that parents might question the approach, but notes that the preemies always could be whisked into standard care if they fared poorly in the new system.