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…


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.



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