A prediction model for superimposed preeclampsia in women with chronic hypertension during pregnancy

Objective: Women with chronic hypertension are at increased risk for superimposed preeclampsia. We developed a prediction algorithm for superimposed preeclampsia using clinical and laboratory information that were measured early in pregnancy. Study design: A secondary analysis of data that were collected from 110 women with chronic hypertension who were enrolled in a trial of calcium supplementation was performed. Blood pressure, the renin-angiotensin system, and calcium metabolism were assessed at 12, 20, 28, and 36 weeks of gestation and 6 weeks after delivery. Multivariable logistic regression was used to develop the predictive model. Results: Thirty-seven women had superimposed preeclampsia. The final model included systolic blood pressure, serum uric acid, and plasma renin activity; which were all measured at 20 weeks of gestation. Women with high systolic blood pressure (> 140 mm Hg), elevated uric acid (> 3.6 mg/dL), and low plasma renin activity (< 4 ng/mL/hr) had an 86% probability of having superimposed preeciampsia. Women with 2 risk factors had a 62% probability of superimposed preeelampsia, and women with only 1 risk factor had a 30% to 40% probability of superimposed preeclampsia. Conclusion: We developed a prediction algorithm that can be validated in future studies for superimposed preeclampsia for women with chronic hypertension. (C) 2004 Elsevier Inc. All rights reserved.