Stress could be linked to miscarriages, researchers have suggested.
It is hoped hormone treatment could reduce miscarriage risk
However, the study published in New Scientist magazine suggests giving at-risk women extra doses of the hormone progesterone could protect pregnancies.
The cause of most miscarriages is never established, but they are usually attributed to abnormalities in the foetus or maternal health problems.
The Miscarriage Association called the University of Berlin study "interesting and possibly very important".
In the initial phase of the research, scientists found that when pregnant mice were deliberately stressed by factors such as loud noise levels, it created an imbalance in hormone levels.
This leads to the immune system more hostile to the foetus, leading to the placenta coming under attack.
The foetus is rejected because its blood supply cannot be sustained.
The researchers found stress hormones such as cortisol are raised in the bloodstream, suppressing the production of progesterone - a hormone which is crucial to the maintenance of a healthy pregnancy.
Falling levels of progesterone lead to a fall in the levels of progesterone-induced blocking factor (PABF) trigger the production of molecules such as interleukin-4 and interleukin-10 within the immune system.
In healthy pregnancies, these molecules tell the immune system to tolerate the foreign cells of the placenta and foetus.
Following the research on mice, the team led by Dr Petra Arck, monitored the progress of 864 pregnant women.
Blood samples were taken at the start of their pregnancies. The women also completed standard questionnaires to measure their own perceptions of the stress they felt.
It was found that the 55 women who miscarried were more likely to have reported stress than women whose pregnancies continued.
The 55 were also more likely to have had lower progesterone and PIBF levels.
Dr Arck said: "We can clearly say that stress has a major impact on pregnancy maintenance."
The scientists were able to prevent the mice miscarrying by giving them an artificial version of progesterone.
The team hopes to carry out research next year looking at whether the same treatment could prevent miscarriages in women reporting high levels of stress, and who have low hormone levels.
The research was presented to a meeting of the British Society for Endocrinology last week.
Dr Alison Douglas, who chaired the conference session where the research was presented, said: "This research is significant because it was a prospective, rather than a retrospective, study of stress and hormone levels."
Ruth Bender-Atik, National Director of the UK's Miscarriage Association, said: "This study is suggesting that stress could be linked to miscarriage, rather than saying it directly causes it."
She said much more work needed to be carried out before the link could be confirmed, and researchers would have to eliminate potential risk factors linked to stress, such as high coffee or cigarette consumption.
"We also have to discover if the low hormone levels are a cause of miscarriage, or an indicator."
But she added: "This is a really interesting, and possibly very important piece of research."