A woman who had ovarian tissue removed and frozen during childhood has given birth to a baby after the tissue was successfully transplanted back into her, enabling her to get pregnant.

The woman, now 27, was only 13 when doctors stored some of her tissue because she was about to have a medical treatment that likely would leave her infertile. Doctors described her case as the first time tissue was removed from someone so young and ultimately led to the birth of a healthy baby.

Born in the Republic of Congo, the woman was diagnosed with sickle-cell anemia, a serious blood disorder, when she was five. She was not identified by the doctors. At age 11, she and her family moved to Belgium and the girl was so sick her doctors gave her a bone marrow transplant from her brother.

Chemotherapy is sometimes used to help stimulate blood production in children with sickle cell anemia, but it risks damaging the ovaries. So the doctors removed part of her right ovary when she was 13 and froze several fragments. The girl hadn't started menstruating but there were other signs she had begun puberty.

A decade later, doctors grafted four parts of the frozen ovarian tissue onto the young woman's remaining ovary and the transplanted tissue later began growing eggs. More than two years afterward, she became pregnant. Last November, she gave birth to a nearly seven-pound baby boy.

"It was a very happy moment," said Dr. Isabelle Demeestere, a gynecologist and fertility researcher at Erasmus Hospital in Brussels. "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." Demeestere and colleagues reported details of the case in a paper published online Wednesday in the journal, Human Reproduction.

Women who had ovarian tissue removed and transplanted have previously given birth, but to date, none were treated in childhood. The transplanted ovaries have typically only worked for a year or two before being removed, Demeestere said.

"We didn't know what would happen when you transplant tissue (back) into a patient that is completely immature," Demeestere said. "But once I saw that she had started ovulating and her hormone profile was normal, I was quite sure she would get pregnant."

Other experts said it was encouraging news but didn't prove that ovarian transplants in children are effective, since the girl had already begun puberty by the time the ovarian tissue was removed.

"There's no reason why it shouldn't work since youngsters survive chemotherapy much better than adults," said Dr. Yacoub Khalaf, director of the Assisted Conception Centre at Guy's Hospital in London.

"To have a child go through this and be able to have a baby years later is just remarkable," said Dr. Jill Ginsberg, a pediatric oncologist at the Cancer Center at the Children's Hospital of Philadelphia. She said these techniques were still experimental and that only a small number of young women would ever qualify for the treatment.

"There is hope for girls who are at high risk of (losing their fertility) but this is still going to be a long shot for anyone going through this kind of treatment," she said.

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