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 wombs into women so they can give birth to their own children.

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

Life-saving 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. Womb transplants — the first ones intended to be temporary, just to allow childbearing — push that frontier even farther and raise some new concerns.

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