Amniotic fluid may hold the key to healing a fatal gut disease which affects premature babies, doctors say.
Severe inflammation, called necrotizing enterocolitis, can destroy the gut's tissues and lead to major organ failure.
Early animal tests, published in the journal Gut, showed that stem cells inside amniotic fluid could heal some of the damage and increase survival.
Further tests are still needed before it is tried in premature babies.
Babies born too soon are not ready for the world outside the womb and their guts are ill-prepared to deal with food. About one in 10 premature babies in a neonatal intensive care will develop necrotizing enterocolitis.
The inflammation can cause tissue death and lead to a hole in the baby's intestines which can result in a serious infection.
Breast milk can reduce the risks, but the only major treatment is surgery to remove the diseased tissue. However, 40% of those needing an operation will not survive.
"It is quite a problem and we think it is on the increase," said Dr Simon Eaton, from the Institute of Child Health at University College London.
He was part of a team investigating the use of stem cells, which are able to become any other type of cell in the body from nerve to bone, taken from the amniotic fluid which surrounds a developing foetus in the womb.
In experiments on laboratory rats, which are programmed to develop fatal necrotizing enterocolitis, injections of stem cells appeared to increase survival times.
Dr Eaton told the BBC news website: "We're able to prolong survival by quite a long way.
"What appears to be happening is a direct effect on calming inflammation and also stimulating resident stem cells in the gut to be more efficient at repairing the intestines."
The study, funded by Great Ormond Street Hospital Children's Charity, showed the intestines were also working better after the treatment.
Fellow researcher Dr Paolo De Coppi said: "Stem cells are well known to have anti-inflammatory effects, but this is the first time we have shown that amniotic fluid stem cells can repair damage in the intestines.
"Although amniotic fluid stem cells have a more limited capacity to develop into different cell types than those from the embryo, they nevertheless show promise for many parts of the body including the liver, muscle and nervous system."
Far more testing would be required to work out if the treatment would work in babies and if it would be safe.
The stem cells would have to be taken from a donor as it would not be practical to store fluid from every birth, just in case. This means there is the risk of rejection.
As the stem cells are capable of becoming other types of cells there is also concern that they may pose a cancer risk.
However, in the future doctors hope they could harness a drug instead.
"It's not the cells, they're delivering something and if we knew what that was then we could deliver that directly," said Dr Eaton.