Risk factors associated with preterm deliveries among racial groups in a national sample of married mothers.

Seven sociodemographic and behavioral factors that may explain the increased risk of preterm deliveries among black women were examined using data from a national sample of 5823 married mothers who responded to the 1980 National Natality Survey (NNS) Questionnaire. There was a twofold increase in the rate of preterm deliveries among black women. Additionally, there was a significant decrease (by 1 week) in the mean gestational age in black mothers (p less than 0.0001) compared with white mothers. The two groups were similar with respect to smoking and age; however, there were significant differences between the two groups with respect to other risk factors. Black women had a higher rate of heavy alcohol use, significantly fewer prenatal visits, prenatal care was started later during pregnancy (p less than 0.0001) and were less educated compared with white women. The odds ratio (OR) for race adjusted for the risk factors was 1.56 (95% confidence interval (CI) equals 1.21, 2.01). All other risk factors except education had adjusted ORs greater than 1. Those risk factors that were more strongly associated with the risk of preterm births included weight gain (OR, 2.10; 95%, 1.79, 2.47), number of prenatal visits (OR, 3.37; 95% CI, 2.87, 3.95) and smoking (OR, 1.34; 95% CI, 1.13, 1.59). We conclude that race is an independent risk factor for preterm deliveries. Additionally, it is shown here that the risk of preterm deliveries is attributable to health behaviors that are amendable to change.