It's a medical first, and one that means some seriously ill young girls won't have to give up on ever having children: A 27-year-old woman in Belgium has given birth to a baby using ovarian tissue that was removed and frozen before she started chemotherapy at 13, the Guardian reports. The treatment for sickle cell anemia—she needed chemotherapy first before a necessary bone marrow transplant—destroyed the function of her remaining ovary, but after the long-frozen tissue was thawed and grafted back into her body, she began menstruating for the first time and was able to conceive naturally and have a healthy baby, the BBC reports. When the tissue was removed, the teenager was showing early signs of puberty but hadn't had her first period, and doctors weren't sure if her eggs would mature.
Around 40 women worldwide have given birth using frozen ovarian tissue, the BBC notes, but this is the first such birth using immature tissue. Researchers say more work needs to be done to determine whether tissue from younger girls can also restore fertility. "There had previously been uncertainty as to whether ovarian tissue taken from young girls would later on be competent to produce mature, fertile eggs, so today's case is both reassuring and exciting," a professor at the Leeds Center for Reproductive Medicine tells Reuters, though he adds: "We have to remember that many children who require chemotherapy are very ill and the surgery to remove ovarian tissue is no small undertaking." (Earlier this year, a British woman born with no womb gave birth to twins.)