The American College of Cardiology/American Heart Association classification of chronic hypertension in pregnancy has better clinical applicability and risk assessment than the traditional severe and mild hypertension approach – lessons from a population-based study

BACKGROUND: Chronic hypertension (CHTN) increases the risk of superimposed preeclampsia, contributing to maternal and neonatal morbidity and mortality. Accurate hypertension classification is therefore essential for risk stratification, antenatal surveillance, prevention, and outcomes. The clinical impact of applying the American College of Cardiology/American Heart Association (ACC/AHA) classification, compared with the American College of Obstetricians and Gynecologists (ACOG) criteria, in pregnancy remains uncertain. OBJECTIVE: To determine the impact of ACC/AHA versus ACOG hypertension classifications on the prevalence of CHTN and pregnancy outcomes. STUDY DESIGN: = 136,606). CHTN was categorized according to ACOG and ACC/AHA criteria. Maternal, fetal, and neonatal outcomes were assessed. Statistical analyses were performed using R-Studio, with ANOVA and Poisson regression models evaluating associations between CHTN severity and outcomes. Under ACOG classification, both mild and severe range CHTN were independently associated with preeclampsia or eclampsia (RR 4.15, 95% CI 3.69-4.65; and RR 3.19, 95% CI 2.82-3.59, respectively). Using ACC/AHA criteria, elevated blood pressure (EBP), stage 1 CHTN (S1CHTN), and stage 2 CHTN (S2CHTN) were each independently associated with preeclampsia or eclampsia (EBP: RR 2.34, 95% CI 2.04-2.65; S1CHTN: RR 4.00, 95% CI 3.56-4.50; S2CHTN: RR 3.32, 95% CI 2.88-3.80). Mild CHTN, S1CHTN, and S2CHTN were independently associated with small-for-gestational-age neonates, while both ACOG-defined CHTN and ACC/AHA-defined EBP, S1CHTN, and S2CHTN were associated with preterm birth. CONCLUSION: Application of the ACC/AHA classification identifies a larger proportion of pregnant individuals as having CHTN. Notably, even those with elevated blood pressure had a two-fold increased risk of preeclampsia compared with the general obstetric population. These findings support the clinical relevance of the ACC/AHA classification in pregnancy and suggest that its implementation may improve identification of patients who may benefit from targeted preeclampsia prevention strategies.