TOKYO (Yomiuri Shimbun/Asia News Network) - A 30-year-old woman in Japan has given birth to a baby after undergoing in-vitro fertilisation (IVF) treatment using one of her eggs that had been frozen for 12 years, according to sources.

It is rare for a woman to have a successful pregnancy in cases where an egg has been preserved for more than 10 years, an expert said.

The egg was taken from the woman just before she underwent cancer treatment as a high school student.

The woman had developed malignant lymphoma, a type of blood cancer, when she was a first-year high school student, said Masashige Kuwayama, head of Repro-Support Medical Research Centre in Shinjuku, Tokyo, who was involved in the freezing of the woman's eggs.

As it was feared that she could become sterile due to chemotherapy, two of her eggs were extracted at a fertility treatment clinic in 2001 when she was a second-year high school student. The eggs were then frozen and preserved.

The woman, who overcame malignant lymphoma with the chemotherapy, got married last year. She underwent IVF using her husband's sperm and two eggs that were thawed. One of the fertilised eggs was implanted in her womb, and she gave birth to a 3.3-kg boy in August.

The woman has said through a patient support group that she hopes her case will encourage other cancer patients.