Doctors in Sweden claim they have performed the first mother-to-daughter womb transplants which they hope will increase the chances of the recipients having a baby.
The operation to transplant the wombs was a success according to the surgeons but the procedure won't be considered a complete success until the women successfully conceive.
"That's the best proof," Michael Olausson, one of the surgeons told the Associated Press.
One woman lost her womb to cervical cancer the other was born without a functioning womb. They are 37 and 32 but have not been named.
They chose to use the women's mothers as donors because it reduces the risk of their bodies rejecting the donated womb. They can also be confident the donor wombs are healthy as each previously carried a child to full-term.
If they do concieve their babies will be in the unprecedented situation of developing in the same womb that carried their mothers. But rather than be an inpediment to the proceedure the surgeons hope the "emotional connection" between mother and daughter will help.
A year's recovery
After a year's recovery from the operation the women will undergo IVF treatment to see if they can conceive.
These are not the world's first womb transplants. Saudi surgeons transplanted a uterus from a living donor in 2000 but the proceedure failed after three months.
Last year, Turkish doctors transplanted a womb from a deceased donor but it is not yet known whether the recipient has conceived.
Other researchers are cautious. A womb that is foreign to the rest of a mother's tissues or the effects of anti rejection drugs could effect the development of any baby that is conceived.
Problems with the placenta developing properly or with premature birth are both major risk factors with the procedure.
One research team in New York abandoned work on womb transplants because of poor success. Fertility expert James Grifo of New York University found problems with immuno-suppressive drugs.
"The group of patients that would need this is so small we decided to focus our efforts elsewhere," he told the Associated Press. "We started in rats, but once we got to humans, it became very clear the rejection drug was going to be the issue, and we didn't know how to safely deal with that issue."
The Swedish researchers say their work on rats and pigs show no problems with anti-rejection drugs. They also point out other transplanted organ recipients who take the medicines have been able to conceive normally.