|Feb. 20, 2006
ANN ARBOR, Mich. - Women who exhibit signs of
stress are three times more likely to miscarry during the first
three weeks of the pregnancy, a recent study of a small population
of women found.
Pablo Nepomnaschy and a group of University of
Michigan researchers measured the cortisol - a stress induced
hormone - levels in urine samples taken three times weekly for a
year from 61women in a rural Guatemalan community. Nepomnaschy
conducted the fieldwork while he was a Ph.D student at U-M both at
the Anthropology Department and the School of Natural Resources and
Environment. He is now a post-doctoral fellow at the Epidemiology
Branch of the National Institute of Environmental Health Sciences.
The Guatemalan study is the first to link
increases in cortisol levels to very early-stage pregnancy loss.
According to previous scientific reports
anywhere from 31 percent to 89 percent of all conceptions result in
miscarriage. Most studies begin when women notice they are pregnant,
about six weeks after conception. Most miscarriages, however, are
known to happen during the first 3 weeks of pregnancy.
"The only way to capture the first three
weeks of pregnancy is to begin collecting their urine from before
they become pregnant. That is extremely labor intensive and
expensive," Nepomnaschy said.
In the Guatemalan study, 22 pregnancies
occurred in a total of 16 women, and each woman's cortisol levels
were measured against their own baseline levels. Researchers found
that 90 percent of women, whose ages ranged from 18 to 34, with
elevated levels of the stress-induced hormone miscarried during the
first three weeks of pregnancy, compared to 33 percent of those with
The body may recognize the elevated cortisol
levels as an alarm that conditions are unfavorable for pregnancy.
"Maybe increased cortisol is understood
by the body as a cue that the context is uncertain, changing, or the
quality of the environment is deteriorating," Nepomnaschy said.
"The body's response is to stop any extra activity and go back
to its most basic functions."
Given that previous studies focus on later
pregnancy stages did not find an association between elevated
cortisol and miscarriage, Nepomnaschy and colleagues speculate that
stress may be more likely to lead to loss during the earliest stages
of pregnancy, while the embryo is just beginning to develop. They
caution, however, that more research is necessary on this topic
before definitive conclusions can be reached.
Its unclear if cortisol is directly involved
with the miscarriages or if it signals some other mechanism in the
body that causes the miscarriage. However, the results are
consistent with a 2004 study in which Nepomnaschy his colleagues
found that elevated cortisol levels were associated with lower
progesterone levels - a hormone that prepares the uterus for the
implantation of the fertilized ovum.
"The two pieces of research are
consistent in this sense," Nepomnaschy said.
The next step, Nepomnaschy said, is to attempt
to replicate these results in a larger population.
Co-authors on the Guatemalan study include
Kathleen Welch, Center for Statistical Consultation and Research;
Daniel McConnell, Department of Epidemiology and the Reproductive
Sciences Program; Bobbi Low, SNRE; Beverly Strassmann, Department of
Anthropology and the Research Center for Group Dynamics; and Barry
England, Department of Pathology and the Reproductive Sciences