US researchers say stem cells nearly as powerful as embryonic stem cells can be found in the amniotic fluid that protects babies in the womb.
They have used them to create muscle, bone, fat, blood vessel, nerve and liver cells in a laboratory, and say they believe the placenta and amniotic fluid can provide one more source of the valued cells, which scientists hope will some day transform medicine.
Scientists say they would also provide a non-controversial source of the cells, which are found with difficulty throughout the body and in days-old embryos.
"Embryonic cells are considered the most malleable of the various types of stem cells, but these amniotic fluid-derived cells are a close second," said Dr Anthony Atala from the Institute for Regenerative Medicine.
"Our hope is that these cells will provide a valuable resource for tissue repair and for engineered organs as well.
"I feel these cells are pluripotent like human embryonic stem cells."
Pluripotent means the cells can give rise to any type of tissue in the body, including blood, nerve and muscle.
Adult stem cells, found in the tissues and blood of foetuses, babies and adults, are already partly differentiated and are less adaptable.
The use of human embryonic stem cells is controversial in some countries, including Australia and the United States.
US President George W Bush has restricted federal funding of human embryonic stem cell research, although researchers using private money can do as they please and Congress, even before the Democrats took over, was planning ways to encourage more research.
