Doctors have treated a baby with brittle bone disease while still in the womb.

The foetus, which had been diagnosed with Osteogenesis Imperfecta (OI), was treated using stem cell technology.

The Swedish team took genetically unmatched cells from another foetus to treat the unborn girl, who is now two-and-a-half years old.

Osteogenesis Imperfecta leaves sufferers especially prone to fractures, but the girl has suffered just three since receiving the stem cell therapy in the womb.

Researchers at the Karolinska Institute researchers stressed that stem cell therapy was not a cure for OI, or brittle bone disease. Stem cells are very primitive cells that have the capability to become any cell in the body.

"The big advance is that we have given stem cells that are completely unmatched and they have not been rejected," lead investigator Celia Gotherstrom said.

"It means we could give stem cells from any person to another person."

The results suggest that fetal mesenchymal stem cells may be a valuable source for transplantation and cell therapies.