Background: Rates of preterm delivery in the United States are higher in black women compared with whites. In this study, we examined cardiovascular reactivity and risk of preterm delivery among black and white military women.
Methods: We recruited a total of 500 black and white active-duty military women from the prenatal clinic at a large military installation, interviewing them early in pregnancy and again at 28 weeks of gestation. A subgroup of women underwent a computerized stress test to determine cardiovascular reactivity assessed as increases in heart rate and blood pressure compared with measurements taken before the stress test.
Results: Despite a relatively low overall risk of preterm delivery (8.2%), we found the same 2-fold racial disparity reported in other populations (hazard ratio for preterm delivery in black women vs whites = 2.30; 95% confidence interval = 1.24-4.27). The disparity is present in all military ranks and is largest for medically indicated preterm deliveries. Among the 313 subjects who participated in the computerized stress testing, blacks exhibited more cardiac reactivity than whites. In black subjects only, a 1-mm increase in diastolic blood pressure reactivity was associated with 1.1 a day earlier delivery (-0.17 weeks). A similar trend was seen with heart rate.
Conclusions: Autonomic dysfunction after exposure to stressors may play a role in the timing of delivery among black women.