Extremely premature lambs grew, apparently normally, inside the system, for three to four weeks. “We start with a tiny fetus that is pretty inert and spends most of its time sleeping. Over four weeks we see that fetus open its eyes, grow wool, breathe, swim,” said Dr. Emily Partridge, first author of the study published in Nature Communications. Human testing still is three to five years away, although the team already is in discussions with the Food and Drug Administration. Hospitals attempt to save the most critically premature infants, those born before 26 weeks gestation and even those right at the limits of viability, 22 to 23 weeks, knowing that extreme prematurity is a leading cause of infant mortality, in the world. The device , called “Biobag”is simpler than previous attempts at creating an artificial womb. The study however didn’t address long-term development.