Job stress: a risk for pregnant workers?

A pilot study indicates that pregnant women in high-stress jobs secrete elevated amounts of catecholamines, the socalled "fight-or-flight" hormones. Some scientists suspect that elevated blood levels of these hormones can sometimes trigger premature labor and early delivery of very small babies, who risk breathing troubles and other serious health problems.

The new report may help explain previous findings linking stressful jobs with an increased threat of premature labor and delivery of low-birthweight babies. Experiments with pregnant animals have shown that elevated catecholamine levels can decrease blood flow to the uterus, in some cases leading to premature labor.

Obstetrician Vern L. Katz noticed among his patients that pregnant physicians with demanding work schedules seemed to deliver prematurely more often than women in less stressful jobs. That observation prompted Katz and his colleagues at the University of North Carolina in Chapel Hill to explore the connection between catecholamines and stress in a study of 10 physicians and three intensive-care-unit nurses, all in their third trimester of pregnancy. The 13 women had jobs requiring long and irregular shifts, prolonged periods of standing, and mentally taxing duties such as decisions about patient care.

The researchers instructed the women to collect urine samples during a typical workday and again, about a week later, on a non-workday. In analyzing the urine samples, the team discovered that catecholamine levels averaged 58 percent higher on workdays than on non-workdays.

They went on to compare these levels with those of a control group of 12 women in their third trimester os pregnancy who worked in lower-stress jobs. The 12 women collected urine during a typical workday, and again the team analyzed the samples for catecholamines.

In the March Obstetrics & Gynecology, the researchers report that workday catecholamine values among the group percent higher then those of the lower-stress group.

The investigators emphasize that their small study is only a pilot and does not settle the troubling question of whether on-the-job stress can cause difficult pregnancies. "I certainly wouldn't want anyone to think that we've found the link between work and poor pregnancy outcome," says study co-author Watson A. Bowes Jr. Katz addst that stress may represent just one of many factors that could increase the risk of premature labor and other pregnancy problems.

Indeed, the team has yet to show that elevated levels of stress hormones in pregnant women can precipitate premature delivery or difficulties during gestation, says obstetrics researcher A. Brian Little of McGill University in Montreal. In a larger study, Katz and his colleagues hope to determine whether catecholamine levels affect the risk of such problems.

Research reported last fall indicated that highly stressed female physicians ran no greater risk of preterm delivery than a control group of women with less stressful jobs. However, the study did reveal that premature labor - which often requires bed rest or hospitalization to prevent early delivery - was twice as common among female physicians than among the controls, according to a report in the Oct. 11, 1990 New England Journal of Medicine.

The report's lead author, Mark A. Klebanoff of the National Institute of Child Health and Human Development in Bethesda, Md., concludes that working long hours in a stressful environment has "little effect on the outcome of pregnancy in an otherwise healthy population." Klebanoff concedes that increased catecholamine levels may contribute to the higher incidence of early labor found in his study, but he says further research must prove that link.