A Japanese team led by St. Luke¡¯s International Hospital has said that two women have successfully given birth using transplanted ovarian tissues that had been frozen before they underwent cancer treatment.

As balancing cancer treatment and pregnancy has been a challenge, this example of pretreatment ovarian tissue preservation resulting in birth may garner attention. The team announced the successful cases in an international medical journal.

One of the two individuals entered menopause before the age of 20 and the other during her 20s, due to treatment for Ewing sarcoma, a rare form of cancer. They both had one ovary removed and cryopreserved before starting their cancer treatment.

Once they were in remission following their treatment and judged to be able to conceive, the ovarian tissues were transplanted.

The team adopted a ¡°circular string arrangement¡± technique, in which ovarian tissue fragments are placed in a shape similar to a beaded necklace within a space created in the peritoneum near the uterus. By keeping the stitches to a minimum, the team aimed to prevent blood flow problems and tissues overlapping, so as to encourage engraftment.

After the transplants, the two women¡¯s ovarian functions recovered and menstruation restarted. They became pregnant through in vitro fertilization involving the collection of eggs multiple times and embryo transfers. They both gave birth in 2025.

Depending on the urgency of cancer treatment and the age of patients, there are cases in which eggs and fertilized eggs cannot be frozen before the start of treatment.

While cases of cancer patients¡¯ pregnancies and births after ovarian tissue transplantation have been reported in Japan, it is rare that post-transplant pregnancies and childbirths by those who entered menopause due to cancer treatment have been closely monitored.

Tetsuya Hirata, a doctor at St. Luke¡¯s International Hospital, voiced hopes of verifying the transplant technique¡¯s efficacy and safety by handling more such cases. The technique ¡°may become an option (for cancer patients) to balance treatment and future pregnancy,¡± he said.