Giuseppe Del Priore has the appearance and the soft-spoken, compassionate manner of a well-paid New York doctor. Just the type, in fact, that a woman might trust to stitch a new uterus into her barren abdomen.

Further work is needed before a uterus transplant can safely be used to help infertile women bear a child. Credit: S. CAMAZINE/SPL

And that is exactly what Del Priore, an obstetrician and gynaecologist at New York Downtown Hospital, hopes to do, along with Jeanetta Stega and other colleagues. A spate of recent media reports has highlighted their plans to provide an infertile woman with a transplanted uterus so that she might bear a child — an operation that, if performed, would be only the second such attempt in the world.

A transplant could potentially help some of the most intractable cases of infertility, such as women born without a uterus, those who underwent a hysterectomy at a young age because of cancer or fibroids, or those in whom an infection has closed up the organ. Many such women are desperate to have their own biological children, and the only way for them to do so at present is by having one of their embryos implanted in a surrogate mother — which is illegal in many countries.

But some researchers and bioethicists are voicing concern about the prospect of uterus transplants. They argue that the risks are unknown and that the technique may be moving too fast into the clinic. “It's hard to think of another way [of bringing a child into a family] that would be more physically risky or expensive,” says Thomas Murray, director of the Hastings Center, a bioethics research institute in Garrison, New York. If a member of his own family was considering it, he adds, “I'd do everything in my power to talk her out of it.”

In a uterus transplant, the organ would be removed from a living or recently deceased donor and transferred to a recipient. Embryos previously created by in vitro fertilization would be transferred to the uterus and, after a child was born, the uterus would be removed to avoid a lifetime of taking powerful immunosuppressant drugs to prevent rejection.

Del Priore says he realized that the operation was feasible after helping to pioneer a surgical technique for cervical cancer that preserves the uterus. In this process, he explains, the uterus is virtually removed from the body, as it would be during a transplant, but is then reconnected. Many women who have had such a procedure have gone on to have healthy babies.

I think technically it can be done, but I say that with a great deal of caution, because it's a huge undertaking.

A human uterus transplant has already been done, in Saudi Arabia in 2000, but it had to be removed after 99 days because of a dangerous blood clot1. Most researchers, including Del Priore, say that before attempting the procedure in humans they want to gather more evidence that they can perform three crucial steps in animals: obtain a uterus, transplant it, and show that it can bear healthy offspring. “Yes, I think technically it can be done, but I say that with the greatest deal of caution, because it's a huge undertaking,” Del Priore says.

Another leading researcher in this small field, Mats Brännström of Gothenburg University in Sweden, showed more than three years ago that mice could bear babies from a transplanted uterus. However, the donor and recipient were virtually genetically identical, so rejection was not an issue2. Since then, his team has successfully removed the uterus of a sheep, then replaced it in the same animal, he says. He believes she is now pregnant.

But animal experiments such as these are not ideal models for a human transplant because the uteri have a different anatomy and, in the case of mice, rabbits and pigs, they support multiple fetuses whereas a woman's uterus typically holds only one or two. So Brännström and others say they want to trial the operation in primates before starting in humans.

Stefan Schlatt of the University of Pittsburgh in Pennsylvania, who is collaborating with the New York team, says he has tried and failed to perform the transplants in macaques. He adds that he has just received approval for a further two attempts. If primate experiments succeed, human ones are likely to follow quickly. “Once we show the first monkey baby, people will step up and say they want to do it,” Schlatt says. “People are so desperate to have children, they wouldn't wait for ten babies to be born to show it's safe.” Researchers interviewed by Nature estimate that a human operation could take place within two to five years.

Del Priore says he wants to accumulate animal data and gain more experience with human surgery before trying a human transplant: “Somehow we hope we'll know when it's right.” But there is no consensus on what experimental data are required before a human operation is considered an acceptable risk.

The group is already laying the groundwork with donors and recipients. Earlier this year, they showed that it was possible to remove a healthy human uterus from a brain-dead organ donor whose heart was still beating3. The researchers are now compiling a list of interested recipients who are being sent information and consent forms to say they are willing to be evaluated for the procedure. The team says the evaluation process will include a psychological assessment and an explanation of alternatives such as adoption.

Del Priore and his colleagues say they are motivated by the number of infertile women who are keen to undergo the operation and who understand the risks. But some bioethicists question how much of the work is really fuelled by doctors' ambition and ego — particularly in the fields of transplant surgery and reproductive medicine, both renowned for aggressively pursuing new methods. “It's a heady cocktail; it brings together two of the more adventurous branches of medicine,” says Murray.

Most transplants performed today — such as heart, lung and kidney transplants — are to cure life-threatening or critical conditions. There have been a few exceptions, such as the first face transplant last year, but these are controversial because it is difficult to judge whether the benefits of such transplants are outweighed by the risks.

In the case of uterus transplants, the risk–benefit calculation is even more complex as it must also factor in unknown threats to the future child. Although many thousands of children have been born worldwide to women who have received other transplants, some transplant recipients seem to be at increased risk of pregnancy complications such as high blood pressure and premature birth. It is also not known whether the immunosuppressant drugs might cause subtle effects that become apparent only when the children grow up4.

Murray suggests that bodies such as the American College of Obstetricians and Gynecologists should investigate the procedure in order to guide future research. An international symposium on uterine transplantation is to be held in Gothenburg in April. “I'm enthusiastic about the possibility of treatment,” says Per-Olof Janson, a gynaecologist at Gothenburg University who is co-chairing the meeting, “but I'm hesitant about rushing.”