A group of University of Michigan researchers measured the cortisol levels – a stress induced hormone – in urine samples taken three times weekly for a year from 61 women in a rural Guatemalan community.

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 three 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 labour intensive and expensive," said Pablo Nepomnaschy, who conducted the fieldwork.

In the Guatemalan study, 22 pregnancies occurred in 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 normal levels.

The body may recognize the elevated cortisol levels as an alarm that conditions are unfavourable 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, the researchers 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.

MEDICA.de; Source: University of Michigan