The concept behind the new artificial womb is fairly simple: fetal lambs were placed inside a soft, temperature-controlled plastic bag filled with amniotic fluid to mimic a real uterus and their umbilical cords were hooked up to a blood oxygenating machine. Unlike previous devices, however, the Philadelphia team's artificial womb uses the animal's own heart to circulate blood, rather than mechanical pumps which can hurt the animal and lead to development problems or lung issues later on.

As Alan Flake, the director of the hospital's Children's Institute for Surgical Science, told reporters, the device won't replace a real, living uterus just yet because it can't replicate the earliest stages of development. But for infants born around 22 or 23 weeks -- the earliest a premature child can be expected to survive outside the womb -- the new device presents a better solution than the incubators currently in use in neonatal wards. At the start of the test, the fetal lamb test subjects were roughly the same gestational age as a critically premature human fetus. After four weeks, however, eight lambs were "born" out of the sacks with normal, healthy development and lung function on par with a mature infant.

According to Flake, his research team has already been in contact with the US food and Drug Administration and trials of the device could start sometime in the next three to five years. The device itself, however, will likely get a less alarming and more "parent-friendly" redesign in the process, Flake said.