A 27-year-old woman gave birth to her first child after doctors successfully restored her fertility by transplanting the ovarian tissue that was removed from her when she was a child. This is the first case of an ovarian tissue transplant to use tissue taken from a girl before puberty.

"This is an important breakthrough in the field because children are the patients who are most likely to benefit from the procedure in the future. When they are diagnosed with diseases that require treatment that can destroy ovarian function, freezing ovarian tissue is the only available option for preserving their fertility," said Dr Isabelle Demeestere, a gynecologist and research associate at the Fertility Clinic and Research Laboratory on Human Reproduction at Erasme Hospital in Brussels, in a press release.

The patient was nearly 14 years old when doctors removed her right ovary prior to a bone marrow transplant because the chemotherapy could cause permanent damage on the ovaries. After removal, the doctors froze her ovary's tissue fragments. The transplant was successful and her sickle cell anemia improved, but doctors had to put her under hormone replacement therapy to induce the onset of menstruation.

At 24, the patient said she wanted to become pregnant. Although uncertain if it would work, the team used her frozen ovarian tissue to form a right ovary.

Even the doctors were amazed when the tissue started growing follicles containing eggs. Two years after the ovarian tissue transplant, the patient got pregnant and gave birth to a healthy baby boy weighing 6.7 pounds.

The study findings were published in the June 10 issue of the journal Human Reproduction.

The procedure received positive feedback from fertility experts.

"This is a major breakthrough. It is one anecdotal case, but it's immensely exciting. It demonstrates a natural conception and a healthy baby in a woman who simply would not have had this option until now," said Dr. Geeta Nargund, medical director at the U.K.'s Create Fertility, to the Guardian. She was not involved in the study.

The researchers admitted that further research is needed to determine if it can become an alternative treatment for fertility issues and a replacement therapy for post-menopausal women. They have another patient who underwent the same procedure and now has two babies.