The transplant was carried out using keyhole surgery

Melanie Morgan has had three children, but Stephanie Yarber is infertile.

Doctors in Missouri removed tissue from Melanie's ovary and attached it to Stephanie's in a five-hour ovarian graft operation.

Ovarian grafts usually use a woman's own tissue, rather than a donor's, re-implanting it after treatment which could have affected fertility.

Patients may have had cancer treatment or surgery which could have affected their ability to have children.

It takes a special person, but that's Melanie   Stephanie Yarber

Stephanie and her husband spent $10,000 on IVF, without success.

A team led by fertility expert Dr Sherman Silber, director of the Infertility Center of St. Louis at St. Luke's Hospital Missouri, carried out the ovary transplant on the 24-year-old sisters from Muscle Shoals, Alabama.

'No rejection'

Doctors used keyhole surgery to remove one of Melanie's ovaries. They then removed the outer tissue, which is rich with egg-producing follicles.

That tissue was then microsurgically sutured to each of Stephanie's ovaries.

Dr Silber said he expected Stephanie to start menstruating in three months and then, hopefully, to be able to become pregnant.

He added: "This will require no follow-up, no in vitro fertilisation, no donor eggs. It's a perfect situation. There won't be rejection."

But Dr Silber said the donor graft technique could not be widely used to help woman with fertility problems because they would need to take potentially dangerous drugs to prevent them rejecting ovarian tissue from a donor.

Stephanie will not require anti-rejection drugs was because her donor was her identical twin.

After the operation, Stephanie praised her sister for what she had done.

"We are very close. It takes a special person, but that's Melanie. She didn't hesitate when I asked her about it."

Fertility clues

Doctors hope that, by studying Stephanie and Melanie closely, they can understand why she became menopausal at just 13.

Dr Silber added: "Those genetic answers will give us clues to what causes female infertility.

"With this extremely rare set of twins, it's an enormous opportunity to isolate and study the genes that supply eggs.

"It's key to determining the fertility of women as they get older."

Dr Adrian Lower, a consultant gynaecologist and medical director of Isis Fertility Centre in Colchester, told BBC News Online "Stephanie could start to try to conceive straight away. If the surgery has worked, she will start ovulating within a month."

He added: "The surgery itself is relatively straightforward. But the problem is that if you are doing it on an unrelated patient you would have to give immuno-suppressant drugs to prevent rejection and these drugs can affect ovulation.