A dozen babies have been born using a naturally occurring hormone, kisspeptin, which stimulates women's ovaries to produce eggs.

The births, reported in the Journal of Clinical Investigation, show the hormone can be used successfully. Fertility researchers hope kisspeptin will prevent ovarian hyperstimulation syndrome (OHSS), but larger trials are needed to fully assess safety.

A hormone, hCG, is normally used to produce a few eggs for IVF. But in around 10% of patients, the ovaries go into overdrive and produce too many. The condition can lead to kidney failure and potentially death.

In 2003, UK researchers discovered kisspeptin. It is heavily involved in the menstrual cycle and people without the hormone will not go through puberty. The team at Imperial College London believe kisspepin would stimulate the ovaries in a gentler, more natural way that would prevent OHSS.

The first human trials have been taking place on 53 volunteer couples at Hammersmith Hospital in London.

Eggs were successfully collected from 51 women, of whom 12 have since given birth. Prof Waljit Dhillo, of Imperial College London, told the BBC: "The first patient who went through the study got pregnant. It was the best outcome you could have wanted, it was a really triumphant moment.

"We think it should be safer. We've now shown it is effective, but we need larger studies."