Nine women in Sweden have successfully received transplanted uteruses donated from relatives in an experimental procedure that has raised some ethical concerns. The women will soon try to become pregnant with their new wombs, Dr. Mats Brannstrom, the leader of the pioneering project, has revealed.

The women were born without a uterus or had it removed because of cervical cancer. Most are in their 30s and are part of the first major experiment to test whether it's possible to transplant uteruses into women so that they can give birth.

In many European countries, including Sweden, using a pregnancy surrogate isn't allowed.

Lifesaving transplants of organs such as hearts, livers and kidneys have been done for decades, and doctors are increasingly transplanting hands, faces and other body parts to improve patients' quality of life. Uterus transplants — the first ones are intended to be temporary, just to allow childbearing — push that frontier even farther.

There have been two other attempts to transplant uteruses — in Turkey and Saudi Arabia — but both failed to produce babies. Scientists in Britain, Hungary and elsewhere are planning similar operations, but the efforts in Sweden are the most advanced.

"This is a new kind of surgery," Brannstrom told The Associated Press in an interview from Goteborg. "We have no textbook to look at."

He said the nine uterus recipients are doing well. Many already had their periods six weeks after the transplants — an early sign that the wombs are healthy and functioning. One woman had an infection in her new uterus, and others had some minor rejection episodes, but none of the recipients or donors needed intensive care after the surgeries, he said. All left the hospital within days.

The operations did not connect the uteruses to the fallopian tubes, so the women are unable to become pregnant naturally. But all who received a womb have their own ovaries. Before the transplants, the women had some eggs removed and fertilized in vitro. The embryos were then frozen, and doctors plan to transfer them into the new uteruses, allowing the women to carry their biological children.

The transplants have ignited hope among women unable to have children because they lost their uterus to cancer or were born without one. About 1 in 4,500 women is born with a syndrome, known as MRKH, in which she doesn't have a uterus.

Fertility experts have hailed the project as significant but stress it's unknown whether the transplants will result in healthy babies.