Some women who have recurrent miscarriages might benefit from taking a tablet designed to treat diabetes, researchers say.
A trial in 38 volunteers suggests it helps better prepare the womb lining for pregnancy by boosting certain beneficial cells.
Experts believe some women who miscarry do not have enough of these stem cells.
Cally Cusack, now a mother of two, is one of the women in the trial the drug, sitagliptin, may have helped.
Cally, 29, from Doncaster, did not know until after the study had finished she had been given the real drug rather than a placebo pill.
She had had four miscarriages in the past.
And she and partner, Joshua, had almost given up hope of having their own baby.
"We had got to the point when we did not think it was going to happen for us and we had started looking into adoption," she said.
"But then we were offered the chance to take part in this trial.
"We decided to give it a go.
"We figured that even if it didn't help us, at least it might help somebody else."
After three months on the drug, Cally's stem-cell count in her womb lining had improved. She then became pregnant and nine months later had her first son, Dawson, who is now nearly two.
"Throughout the entire pregnancy, you are on eggshells. I had lost four at various stages, between six and 14 weeks gestation.
"To get to the end and have Dawson - we were absolutely elated. It's the most amazing feeling. I can't really describe it."
One of the researchers, Prof Siobhan Quenby, from the University of Warwick's Medical School, said it was too early to say if the drug could prevent miscarriages - larger studies were needed to confirm that - but the treatment did appear to boost stem-cell numbers in the womb lining to support the placenta, which was "very exciting".
"It basically helps the body to repair itself," she said.
"It's a step towards finding a new cure for miscarriage - and that's why I'm so excited."
Stem cells are immature cells that can become many types of tissue.
And experts believe a lack of stem cells in the womb lining could be causing thousands of women to have recurrent miscarriages - the loss of two or more consecutive pregnancies in the first 24 weeks.
But there are many other reasons why someone might miscarry, including abnormalities in the developing baby. And the drug would not help with these.
Often, a cause is not identified.
About one in four women will experience a miscarriage in their lifetime. One in 100 will have multiple miscarriages. The vast majority of women go on to have healthy babies.