Preeclampsia Associated with Chronic Hypertension Among African-American and White Women

Objective: To examine the racial differences in preeclampsia/eclampsia (preeclampsia) associated with chronic hypertension among African-American and White women. Methods: Using hospital discharge summary records from the National Hospital Discharge Survey from 1988 to 1996, we conducted a case-control study to assess the risk of preeclampsia among women with chronic hypertension in two separate identical models: one for African-American and another for White women. Cases were pregnant women who developed preeclampsia. Controls were women without preeclampsia. The main exposure was chronic hypertension. Logistic regression was used to derive odds ratios (OR) and 95% confidence intervals (CI) and to assess interaction between hypertension and preeclampsia. Population attributable risk percent associated between chronic hypertension and preeclampsia was calculated for each ethnic group. Results: Preeclampsia was more than eleven times likely among women with chronic hypertension compared to normotensive women for both African-American (OR = 12.4, 95% CI = 10.2-15.2) and White women (OR = 11.3, 95% CI = 9.7-13.2). Among African-American women, we found an interaction between chronic hypertension and region on preeclampsia. The effect of region magnified the risk of preeclampsia associated with chronic hypertension in general for African-American women, but the effect was lower for the Southern region (OR = 8.9, 95% CI = 6.4-12.3). We also found that the point estimate of population attributable risk percent of preeclampsia attributable to chronic hypertension was significantly higher for African-American women (10.3, 95% CI = 8.6-12.5) compared to White women (5.3, 95% CI = 4.7-6.4). Conclusion: The more than eleven-fold higher risk of preeclampsia among both African-American and White women with chronic hypertension compared to normotensive women underscores the potential risk of chronic hypertension for adverse pregnancy outcomes. Furthermore, the two-fold higher population attributable risk percent of preeclampsia among African-American compared to White women quantifies the burden of preeclampsia attributable to chronic hypertension, and indicates a greater opportunity for prevention.