ObjectiveTo examine effects of maternal hypertension on spontaneous preterm birth (birth at less than 37 weeks' gestation) among black women.MethodsUsing hospital discharge summary records from the National Hospital Discharge Survey between 1988 and 1993, we conducted a case-control study to assess the risk of spontaneous preterm birth among black women with chronic hypertension preceding pregnancy and pregnancyinduced hypertension. Logistic regression was used to derive odds ratios (ORs) and 95% confidence intervals (CIs).ResultsPreterm births were almost two times more likely for women with pregnancy-induced hypertension (OR = 1.8; 95% CI, 1.5, 2.2), more than 1.5 times more likely for women with chronic hypertension preceding pregnancy (OR = 1.6; 95% CI, 1.3, 2.1), and more than four times more likely for women with pregnancy-aggravated hypertension (OR = 4.4; 95% CI, 2.9, 6.7) compared with normotensive women. Preterm births also were associated significantly with antepartum hemorrhage, poor fetal growth, marital status, and source of payment. The odds of preterm birth by mafernal hypertension were increased among women with chronic hypertension and genitourinary infection, whereas the odds of preterm birth were reduced among women with pregnancy-induced hypertension and genitourinary infection.ConclusionThese findings are important in demonstrating the relation between type of hypertension in pregnancy and preterm birth. The relationships between maternal hypertension and preterm birth need to be further investigated to provide some guidelines in the management of hypertension in pregnancy and assessment of prenatal care compliance for black women, particularly when genitourinary infection is present.