Fourteen years ago, a young girl from the Republic of Congo, diagnosed with the debilitating disease sickle cell anemia, was preparing for chemotherapy to increase blood production. Knowing the treatments would leave her infertile, her doctors froze a small portion of her right ovary. Now, following successful transplantation of that same ovarian tissue, the woman has given birth to a healthy baby boy.

Although this procedure has seen success in the past, never before has it been performed using ovarian tissue removed prior to the onset of menstruation. At the time the ovary was removed, the girl was showing signs of puberty onset, but had yet to begin menstruating.

"We didn't know what would happen when you transplant tissue (back) into a patient that is completely immature," says Dr. Isabelle Demeestere, a gynecologist and fertility researcher at Erasmus Hospital in Brussels, who treated the woman. "But once I saw that she had started ovulating and her hormone profile was normal, I was quite sure she would get pregnant."

And two years later, the young woman did just that. She gave birth last November to a nearly seven-pound baby boy.

Back when the chemotherapy was completed, the girl was placed on hormone therapy to induce puberty and kick-start her reproductive cycle. When the girl reached her mid-20s, she decided to try to get pregnant, so the hormone therapy was halted and the surgery to replace the ovarian tissue was scheduled.

Four parts of the ovarian tissue were replanted, which eventually stimulated egg production. Five months later, the girl began menstruating on her own, without the aid of hormone therapy. She became pregnant two years later.

"It was a very happy moment," Demeestere says. "I was most happy for (my patient) because she was afraid if this didn't work, there would be no other option for her to have a baby."

The treatment gives hope for other children who must endure treatments that could leave them infertile.

"It's really quite revolutionary treatment because it's opened up the opportunity for other children who may need to have chemotherapy -- either because they've got diseases of their blood or they may have cancer that needs chemotherapy," says Professor Adam Balen, Chairman of the British Fertility Society. "Now there is the potential to be able to freeze their ovarian tissue, reimplant it when they're adults and enable them to have children, which previously wouldn't have been possible."

The research was recently published in the Oxford University Journal Human Reproduction.