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2004/11/11
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."
BBC NEWS
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