CHAPEL HILL, N.C. -- Pregnant workers who have demanding jobs over which they have little control are more likely to give birth prematurely, according to a new University of North Carolina at Chapel Hill study.
Also, black women appear to at greater risk from job strain than white women, the School of Public Health study indicates. The research is the first U.S. study of pregnancy outcomes and job strain based on detailed interviews with mothers.
A report on the findings appears in the February issue of the American Journal of Public Health, which has just appeared. Dr. Kate M. Brett, a former UNC-CH graduate student now with the National Center for Health Statistics in Hyattsville, Md., led the study for her doctoral degree.
Co-authors of the paper are Drs. David Savitz, chair of epidemiology at the UNC-CH, and David S. Strogatz, a former faculty member now with the N.Y. State Department of Public Health.
"Participation in the paid work force does not itself appear to be detrimental to pregnancy and may actually be associated with a reduced incidence of preterm delivery since women in the work force generally have a more favorable ... profile for good health." the authors wrote. "Working women also tend to have expanded social support and access to medical insurance."
Still, the United States has one of the highest infant mortality rates among industrialized nations chiefly because of preterm and low-birthweight babies, and scientists continue to try to understand why. Psychological stress at home and at work have been suggested as risk factors for preterm delivery, but earlier research uncovered no clear links.
Researchers interviewed 421 N.C. women who delivered infants before 37 weeks gestation and 612 others who delivered on time six months after the babies' births. The researchers then compared the women's birth experiences with descriptions of jobs they held at least month during pregnancy.
After controlling for various potentially complicating factors such as poverty, they found that pregnant women who worked at high-strain jobs full-time or for 30 or more weeks had a moderately increased risk of giving birth early. Overall, the risk was about 40 percent higher for such workers than for women with less stressful, easier jobs.
Job strain has not previously been examined separately by race, the authors said. Black women appear to have less control than white women over their jobs, but also work at somewhat less demanding jobs. Blacks in the groups studied tended to receive less prenatal care and were more likely to smoke cigarettes.
"It appears that work at low-strain jobs outside the home during pregnancy does not increase the risk of preterm delivery," the authors said. "Persistent or full-time employment in a high-strain job may be related to preterm delivery, particularly among black women."
The National Institutes of Health, the Centers for Disease Control and Prevention and the March of Dimes supported the study.