Scientists have created an “artificial womb” in the hopes of someday using the device to save babies born extremely prematurely.

So far the device has only been tested on fetal lambs. A study published Tuesday involving eight animals found the device appears effective at enabling 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,” says Alan Flake, a fetal surgeon at Children’s Hospital of Philadelphia who led the study published in the journal Nature Communications.

“They’ve had normal growth. They’ve had normal lung maturation. They’ve had normal brain maturation. They’ve had normal development in every way that we can measure it,” Flake says.

Flake says the group hopes to test the device on very premature human babies within three to five years.

“What we tried to do is develop a system that mimics…