Young women with cancer can face a loss of fertility as a result of their treatment. In response, researchers are trying to make artificial ovaries that could be implanted in women who are experiencing trouble getting pregnant. A team of researchers at Northwestern University led by Ramille N. Shah and Teresa K. Woodruff now reports that it has made a prosthetic ovary by 3-D printing a cross-linked gelatin scaffold and seeding it with isolated ovarian follicles, that house immature egg cells (Nat. Commun. 2017, DOI: 10.1038/ncomms15261). Because the shape of the follicle is crucial for egg maturation and ovulation, the researchers constructed scaffolds with support layers at 30°, 60°, or 90° angles. They found that the follicles survive better in scaffolds with smaller angles and tighter pores because those scaffolds provide more contact points to stabilize the follicles. The researchers implanted the optimized follicle-seeded scaffolds in mice whose ovaries had been surgically removed. After implantation, the mice were able to mate and bear young naturally. The follicles functioned properly, producing the hormones needed for egg maturation, ovulation, and pregnancy. Whether similar artificial ovaries will work in humans remains to be seen because human follicles are more difficult to keep alive after isolation than mouse follicles, says Christiani A. Amorim, a researcher at Catholic University of Louvain who is also trying to make artificial ovaries.