Scientists from the University of Leicester have discovered a way to predict whether a pregnant woman will miscarry.
They believe they have identified a naturally-occurring molecule within the body which can determine whether a woman will suffer a miscarriage.
They said that in cases where women are bleeding in the early stages of pregnancy, those with higher levels of anandamide, a naturally-occurring cannabis, went on to lose their baby.
Forty-five women who showed signs of a threatened miscarriage took part in the study, and all of those who had higher levels of the molecule went on to have a miscarriage.
And of the women the scientists predicted would have a living baby, 94% went on to do so.
Writing in the Journal of the American Medical Association, the university's Professor Justin Konje said he was excited by the findings.
He said: "This is the first stage of this study but the results are very encouraging and we are undertaking further studies to confirm our observations. Once these are confirmed, we plan to develop a bedside test which could then be applied in clinical practice."