A group of infertile women have given birth to 20 children after doctors performed a form of transplant surgery on their eggs.

The technique, developed by a team in Taiwan, involves packing the eggs with mitochondria - the bean-shaped powerplants that generate energy for cells.

It had a dramatic effect, boosting the pregnancy rate in a group of women for whom In-Vitro Fertilisation had failed from 6% per treatment cycle to 35%.

But at least one expert has expressed concern about the safety of the procedure.

The doctors led by Chii-Ruey Tzeng at Taipei Medical University extracted mitochondria from the granulosa cells that surround the eggs. About 3,000 were then injected into each egg.

Mitochondria are unusual because they contain their own DNA. Tzeng believes the method works by replacing mitochondria whose DNA has been damaged.

The research, presented this week at the annual meeting of the American Society for Reproductive Medicine in Philadelphia, was reported in New Scientist magazine.

Because the technique involves adding a woman’s own mitochondria to her eggs it is likely to be less controversial than using those from other women.

In the latter case, children would inherit about 40 of the 25,000 human genes from the donor.

American expert Dr Jacques Cohen, from the Institute for Reproductive Medicine and Science in Saint Barnabas, New Jersey, said the work was impressive but more needed to be done to iron out certain concerns. These included the consequences of moving mitochondria from one cell type to another which, he said, are not understood.