Prevalence of Hypertension Among Pregnant Women When Using the 2017 American College of Cardiology/American Heart Association Blood Pressure Guidelines and Association With Maternal and Fetal Outcomes

IMPORTANCE: Hypertensive disorders of pregnancy are a leading cause of maternal morbidity and mortality. The impact of applying recent guideline definitions for nonpregnant adults to pregnant women is unclear. OBJECTIVE: To determine whether reclassification of hypertensive status using the 2017 American College of Cardiology/American Heart Association (ACC/AHA) guideline definition better identifies women at risk for preeclampsia or eclampsia and adverse fetal/neonatal events compared with the current American College of Obstetricians and Gynecologists (ACOG) definition of hypertension. DESIGN, SETTING, AND PARTICIPANTS: This cohort study used electronic medical record data of women who delivered singleton infants between 2009 and 2014 at a large US regional health system. Data analysis was performed from July 2020 to September 2020. EXPOSURE: Application of ACC/AHA and ACOG guidelines for the definition of chronic and gestational hypertension. MAIN OUTCOMES AND MEASURES: The primary maternal end point was the development of preeclampsia or eclampsia, and the primary fetal/neonatal end point was a composite of preterm birth, small for gestational age, and neonatal intensive care unit admission within 28 days of delivery. Net reclassification indices were calculated to examine how well the lower ACC/AHA diagnostic threshold reclassifies outcomes of pregnancy compared with the current ACOG definition of hypertension. RESULTS: Applying the ACC/AHA criteria to 137 389 pregnancies of women (mean [SD] age at time of delivery, 30.1 [5.8] years) resulted in a 14.3% prevalence of chronic hypertension (19 621 pregnancies) and a 13.8% prevalence of gestational hypertension (18 998 pregnancies). A 17.8% absolute increase was found in the overall prevalence of hypertension from 10.3% to 28.1%. The 2.1% of women who were reclassified with chronic rather than gestational hypertension had the highest risk of developing preeclampsia compared with women without hypertension by either criterion (adjusted risk ratio, 13.58; 95% CI, 12.49-14.77). Overall, the use of the ACC/AHA criteria to diagnose hypertension resulted in a 20.8% improvement in the appropriate identification of future preeclampsia, but only a 3.8% improvement of appropriate fetal/neonatal risk classification. CONCLUSIONS AND RELEVANCE: Using the lower diagnostic threshold for hypertension recommended in the 2017 ACC/AHA guideline increased the prevalence of chronic and gestational hypertension, markedly improved the appropriate identification of women who would go on to develop preeclampsia, and was associated with the identification of adverse fetal/neonatal risk.