A baby is believed to be the first in the world to be born after eggs were taken from his mother and matured in a lab before being frozen, scientists have revealed.
They said the arrival of baby Jules is the first reported case of a baby born after immature eggs were grown outside of the mother and then thawed, fertilised and implanted years later.
Fertility doctors took eggs from the mother, a then 29-year-old French woman, before she started chemotherapy for breast cancer.
But there was not enough time for her to be given ovarian stimulation hormones to help her produce mature eggs that could be frozen.
Instead, the experts removed seven immature eggs from her ovaries and used a technique called in vitro maturation (IVM) to help them to develop further in the laboratory.
They say the case offers hope to women who would like to have children after a cancer diagnosis, but for whom ovarian stimulation is hazardous.
The method also avoids the risk of "re-seeding the cancer", which can happen in some cancers when ovarian tissue is later transplanted back into a cancer patient.
Until now, there have been no successful pregnancies in cancer patients after eggs that have undergone IVM and then been frozen, although some children have been born as a result of IVM followed by immediate fertilisation and transfer to the patient without freezing.
Professor Michael Grynberg, head of the Department of Reproductive Medicine and Fertility Preservation at the Antoine Beclere University Hospital, near Paris, said he and his team are thrilled with the result.
"We were delighted that the patient became pregnant without any difficulty and successfully delivered a healthy baby at term," he said.