LONDON — A woman has made medical history by giving birth after having had an ovary removed and its tissue frozen at age 9, before reaching puberty.

Moaza al-Matrooshi, now 24, was born with beta thalassemia, an inherited blood disorder that was treated with chemotherapy and a bone-marrow transplant when she was a child. Because chemotherapy damages ovaries, her parents had authorized the removal of her right ovary in advance at the University of Leeds.

The medical community celebrated the birth of Ms. Matrooshi’s baby boy on Tuesday in London at the Portland Hospital for Women and Children, saying the event could pave the way to restoring fertility to women who suffer cancer and other illnesses at an early age. Until now, many prepubescent girls who have undergone chemotherapy have had to abandon hopes of bearing children as adults.

Professor Helen Picton, who leads the division of reproduction at the University of Leeds and who oversaw the preservation of the tissue, said that the outer part of the ovary that contained eggs was cut into pieces. The pieces were then placed in liquid nitrogen, she said in a telephone interview, and gradually cooled to a temperature of minus 320 Fahrenheit (minus 196 degrees Celsius), where they remained for 14 years.