Pregnancy and Progesterone
Stress really can cause miscarriages, a series of studies suggests. The good news is that extra doses of progesterone might safeguard the pregnancies of women at risk.
While the cause of most miscarriages is never established, doctors usually attribute them either to abnormalities in the fetus or to illness or health problems in the mother. Most obstetricians dismiss the idea that healthy women can lose healthy babies solely because of stress.
But a series of studies by a team in Germany might change their minds. “We can clearly say that stress has a major impact on pregnancy maintenance,” says team leader Petra Arck of Charité, an institute of the University of Berlin.
The team has shown that when pregnant mice are deliberately stressed by factors such as loud noise levels, this creates hormonal imbalances that make the immune system more hostile to the fetus. It then attacks the placenta.
“That leads to rejection of the fetus because the blood supply can’t be sustained,” says Arck. The chain of events uncovered by her team starts with the release of stress hormones such as cortisol. As cortisol levels rise in the bloodstream, they suppress the production of progesterone, a hormone that is crucial to maintaining a healthy pregnancy.
Falling levels of progesterone cause a fall in progesterone-induced blocking factor. PIBF, Arck found, triggers production of immune-signalling molecules such as interleukin-4 and interleukin-10, which encourage the immune system to tolerate the foreign cells of the placenta and fetus.
Under pressure
But does this apply to humans? Next, Arck monitored the progress of 864 pregnant women. She took blood samples at the start of their pregnancies, and asked them to fill in standard questionnaires to measure their own perceptions of stress.
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She found that the 55 women who miscarried were more likely to have reported stress than the others. And these women were also more likely to have had lower progesterone and lower PIBF levels, Arck told a meeting of the British Society for Endocrinology in London last week.
The results are not conclusive proof that stress increases the risk of miscarriage. “But it’s bound to make it more scientifically plausible,” says Alison Douglas of the University of Edinburgh in the UK, who chaired the conference session.
Arck was able to prevent stressed mice miscarrying by giving them an artificial version of progesterone. In 2005 she hopes to try treating pregnant women with progesterone if they report being stressed and if their progesterone levels are below a certain threshold.
Researchers have already tried using progesterone to prevent miscarriages without success, says Barbara Hepworth-Jones, vice-chair of the Miscarriage Association in the UK. But these studies did not target women suffering from stress, she points out, so this is worth trying. “The more research in this area the better.”
Andy Coghlan