In an experiment at Northwestern University’s Feinberg School of Medicine, researchers successfully printed and implanted synthetic ovaries in mice that resulted in a successful pregnancy.

In 2017, researchers at the Children’s Hospital of Philadelphia created an artificial womb called a “biobag” and used it to successfully keep premature lambs alive and developing normally for 28 days.

We are still years away from synthesizing and growing a full-sized organic womb—but the biobag represents an intervention that could help the thousands of premature babies born before 25 weeks each year.