How Stress Causes Miscarriage
Hormonal Effects on Certain Cells May Trigger Chain Reaction to End Pregnancy
June 5, 2003 -- Stress has long been suspected as a possible
cause of miscarriage, with several
studies indicating an increased risk among women reporting high levels of
emotional or physical turmoil in their early months of pregnancy or just before conception. But while a
relationship has been noted, researchers didn't know exactly how a
woman's stress could cause miscarriage.
In what may prove to be a breakthrough finding, a team of
scientists from Tufts University and Greece have identified a suspected chain
reaction detailing exactly how stress hormones and other chemicals wreak havoc
on the uterus and fetus. Their report, in the June issue of
Endocrinology, may help explain why women miscarry for no obvious
medical reasons and why some women have repeated miscarriages. And it could
lead to measures to prevent miscarriage -- medically known as "spontaneous abortion."
Researchers have long known that during times of stress, the
brain releases several hormones -- including one called corticotropin-releasing
hormone (CRH). In past research, women who deliver prematurely or have
low-birth-weight babies were often found to have high levels of CRH in their
bloodstream, and other studies show a greater risk of miscarriage in women
reporting stress. CRH is a hormone the brain secretes in reaction to physical
or emotional stress, and it is also produced in the placenta and the uterus of
a pregnant woman to trigger uterine contractions during delivery.
But this new research suggests that CRH and other stress
hormones may also be released elsewhere in the body, where it specifically
targets localized mast cells -- those best known for causing allergic
reactions. Mast cells are abundant in the uterus. During stress, the local
release of CRH causes these mast cells to secrete substances that can cause
The Hormone-Allergy Link
In their study of 23 women, the scientists found that those who
had previous multiple miscarriages had significantly high levels of CRH and
another hormone, urocortin, in the tissues of their fetuses when compared with
women who miscarried once or those who had had abortions.
The lead researcher tells WebMD what's especially intriguing is
that high amounts of these stress hormones were found only in uterine mast
cells -- and not in the women's bloodstream, adding credence to his theory that
CRH may be released locally.
"Mast cells are like a soccer ball that is filled with about
500 Ping-Pong balls, and each Ping-Pong ball has about 30 marbles," says
Theoharis C. Theohardies, MD, PhD, of the Tufts University School of Medicine.
"If you are allergic, these cells explode like a grenade to trigger an allergic
reaction by releasing all those balls of histamine and various other
Like an allergen, CRH and urocortin in mast cells may also
release many chemicals. The chemicals known to cause fetal loss were also found
in high amounts in the women studied who had one or more miscarriages.