A seven-year-old girl could one day give birth to her biological half-brother or half-sister after her mother became the first woman to donate eggs to her infertile daughter.

Melanie Boivin, 35, from Montreal, has placed 21 of her eggs on ice for Flavie Boivin to use when she grows up.

Flavie has Turner syndrome, a condition in which one of the two X chromosomes normally carried by women is missing. It almost always causes infertility, though women who have the condition can conceive with donated eggs.

The mother-to-daughter donation is thought to be the first of its kind. Although many infertile women have been given eggs by their sisters, cousins, nieces and even daughters, biology has always prevented mothers from helping their daughters so far. Even if an infertile woman were just 20 years younger than her mother, the donor would likely be in her forties and have poor-quality eggs.

By freezing her eggs while she is still in her mid-thirties and fertile, Ms Boivin hopes to give Flavie a good chance of having children. Were Flavie to rely on an unrelated donor, she would probably have to wait for several years as there is a shortage of donated eggs in most countries, including Canada.

Ms Boivin said: "The role of a mother is essentially to help her children, and if I could do anything in my power to help her I had to do it, and because of my age I had to do it now.

"I told myself that if she had needed another organ like a kidney I would volunteer without any hesitation and it is the same kind of thought process for this."

There is no law in Britain that would stop the mother of a girl such as Flavie from freezing her eggs, but as they can be kept frozen for only ten years it would not usually be practical. This limit, however, could be revised by the time that a child was ready to use the eggs.

Seang Lin Tan, Professor of Obstetrics and Gynaecology at McGill University in Montreal, who led the team that treated Ms Boivin, said that her doctors had referred the case to an independent ethics committee before agreeing to the procedure.

"We were very sensitive to the ethical issue, and had it been the daughter donating to the mother there would have been the possibility of coercion," he told the European Society of Human Reproduction and Embryology conference in Lyons. "But as it was the mother who was going to donate, it was just out of love. It will be up to the daughter whether she uses the eggs in the future."

Another ethics committee would have to approve the use of the eggs should Flavie wish to have them fertilised and implanted, Professor Tan said.

Ms Boivin and her partner, Martin Cote, 35, also have a son, Jeremie, 11, and another daughter, Clara, 2. Clara does not have Turner syndrome.

Josephine Quintavalle, of the embryo rights group Comment on Reproductive Ethics, said: "We have to stop thinking of women only in terms of their reproductive potential."