Stress and blood pressure during pregnancy: racial differences and associations with birthweight.

OBJECTIVE To extend findings that African American women report greater stress during pregnancy, have higher blood pressure (BP), and are twice as likely to have low birthweight infants relative to white women. This study examines a) racial differences in associations between stress and BP during pregnancy, and b) the combined effects of stress and BP on infant birthweight in a sample of 170 African American and white women. METHODS A prospective, longitudinal study of pregnant women was conducted in which measures of BP, stress, and other relevant variables were collected. Multiple measures of systolic and diastolic BP were taken at each of three points during pregnancy (18-20, 24-26, and 30-32 weeks gestation). RESULTS Both systolic blood pressure (SBP) and diastolic blood pressure (DBP) were positively associated with stress in pregnant African American women and not in pregnant white women. In analyses of birthweight, there were no main effects of BP or stress. However, a significant interaction demonstrated that, when stress was high, DBP was negatively associated with birthweight and a combination of high stress and high DBP predicted the lowest birthweight in the sample. Furthermore, African American women were twice as likely as white women to have a combination of high stress and high DBP. CONCLUSIONS Racial differences in relationships between stress and BP, and the interactive effect of stress and DBP on birthweight together suggest that a high stress-high BP profile may pose a risk for lower birthweight among African American women, in particular, and possibly for all pregnant women.