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 miscarriages.
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.