Two Swedish women received new uteruses at the weekend in the world's first mother-to-daughter uterine transplants aimed at helping them have babies, Gothenburg University announced on Tuesday.
Uterine transplants are new, with the first successful one conducted in Turkey in 2011.
"One of the women had previously had her own uterus removed after undergoing treatment for cervical cancer. The other woman was born without a uterus. Both women are in their 30s," a statement from Gothenburg University said.
"More than 10 surgeons took part in the operations, which were conducted without any complications. The women who received the uteruses are doing well but are tired after the surgery," said Mats Braennstroem, a professor of obstetrics and gynecology at the university and the leader of the research team.
"The mothers who donated their uteruses are already up and walking and are going to be able to go home within a few days," he added.
Braennstroem explained at a press conference that the young women would have to wait one year before trying to get pregnant.
They will then undergo in vitro fertilization (IVF) with frozen embryos consisting of their own eggs fertilized with their partner's sperm prior to the organ transplant procedure.
"So we will only really know if this is successful in 2014," if and when the women have given birth to a child, Braennstroem said.
He would not speculate on the chances of the women becoming pregnant, but noted that in regular IVF treatments the chance of delivering a baby after an embryo transfer was 25 to 30 percent.
Braennstroem said the transplanted uteruses would be removed after the women have had "up to two children", so they can stop taking the immunosuppressant medication that helps their bodies accept the transplant.
One of the other doctors on the team, Michael Olausson, said doctors expected the same risk of rejection as seen with other organ donations, of around 20 percent.
The women, whose names were not revealed, were selected for the procedure after a lengthy examination process to ensure she and her partner were fertile and good candidates.
Their mothers were used as donors because of the "theoretical advantage" of having a close relative as a donor, Olausson said, and "because the uterus had proven its functionality in being able to bear a child," Braennstroem added.
Eight more women are due to undergo the procedure in Sweden during the autumn and spring.
Braennstroem stressed the transplant was aimed at helping young women who were either born without a uterus or had a damaged uterus, and not meant to help older women have babies beyond their own child-bearing years.
All of the 10 candidates for the procedure in Sweden are in their 30s or younger, "as IVF has a greater chance of succeeding with younger women," Braennstroem said.
The research team, comprising some 20 scientists, doctors and specialists, has been working on the project since 1999, conducting successful uterine transplants on animals, including mice and primates, that led to births.
Uterine transplants are seen as controversial, primarily because they involve living donors.
The research team was initially blocked by Sweden's Central Ethical Review Board but was given the green light to proceed in May on the condition that it set up a special committee to closely monitor the project.