Association of Mean Arterial, Systolic, and Diastolic Blood Pressure Trends in Early Pregnancy With Superimposed Preeclampsia With Severe Features in Pregnancies Complicated by Chronic Hypertension

OBJECTIVE: To evaluate the association of longitudinal systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP) in early pregnancy with later development of superimposed preeclampsia with severe features in pregnancies complicated by mild chronic hypertension. METHODS: This secondary analysis used data from the CHAP (Chronic Hypertension and Pregnancy) trial, a multicenter randomized controlled trial that involved pregnant individuals with chronic hypertension. Participants were categorized based on the development of superimposed preeclampsia with severe features. Longitudinal blood pressure measurements from enrollment to the development of superimposed preeclampsia with severe features or delivery were assessed using regression models. Separate models were created for SBP, DBP, and MAP to evaluate their associations with the primary outcome. Predictive performance was assessed using area under the curve (AUC) values, the integrated calibration index, and a Brier score. RESULTS: Of 2,316 individuals with chronic hypertension, 600 (25.9%) developed superimposed preeclampsia with severe features. Higher SBP, DBP, and MAP all were associated with superimposed preeclampsia with severe features, with MAP demonstrating the strongest association. Adjusted hazard ratios (HR) indicated that increased MAP, SBP, and DBP were significantly associated with the risk of superimposed preeclampsia with severe features (eg, adjusted HR 1.1556 [95% credible interval: 1.1332–1.1784] per mm Hg increase in MAP). Although MAP showed slightly better predictive metrics compared with SBP and DBP, overall predictive precision remained moderate. The lowest Brier score and highest AUC values were observed for MAP models, though differences among blood pressure metrics were minimal. CONCLUSION: In pregnancies complicated by chronic hypertension, longitudinal MAP trends provide a stronger association with superimposed preeclampsia with severe features compared with SBP or DBP. Although predictive performance was only moderate, these findings support the consideration of MAP as an important component of vital sign monitoring in prenatal care. Further research is warranted to refine risk prediction models through the integration of additional clinical and biomarker data. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov, NCT02299414.