Does Treatment of Mild Chronic Hypertension During Pregnancy Improve Pregnancy Outcomes? The CHAP Study Results

Hypertension during pregnancy is a major cause of maternal morbidity and mortality worldwide and has long term implications for maternal health.1 There has been controversy about the appropriate blood pressure threshold to initiate anti-hypertensive therapy in pregnant individuals with prior consensus only to treat if blood pressure >160/105 mmHg.2 This uncertainty stems from previous trials failing to show clinical benefit of strict blood pressure control beyond decreasing the incidence of severe hypertension and concern about increasing the risk of small for gestational age fetal birth weight.3-5 The objective of the open label randomized controlled Chronic Hypertension and Pregnancy (CHAP) trial was to investigate whether more aggressive blood pressure control improves pregnancy outcomes among pregnant persons with chronic mild hypertension.6

A total of 2,408 pregnant women with chronic hypertension were randomized to a blood pressure goal of <140/90 mmHg or standard care (treatment only if blood pressure >160/105 mmHg). The primary outcome, composite of pre-eclampsia with severe features, medically indicated preterm birth at <35 weeks gestation, placental abruption, or fetal/neonatal death, was significantly lower in the active treatment group compared to the control group (30.2% vs. 37.0% for an adjusted risk ratio of 0.82, 95% confidence interval [CI], 0.74 to 0.9) with no statistical difference in the safety outcome of small for gestational age birth weight. Importantly, a considerable proportion of the study population was non-Hispanic Black (47.5%).

The CHAP trial is a landmark trial that addresses an important clinical question about the treatment of chronic mild hypertension during pregnancy. The results support the treatment of blood pressure to a target of <140/90 mmHg in pregnancies complicated by chronic hypertension. Based on these results, the American College of Obstetricians and Gynecologists (ACOG) released a practice advisory recommending treatment of chronic hypertension during pregnancy to a goal of <140/90 mmHg.7 Future studies are needed to assess optimal implementation strategies to achieve adequate blood pressure control in pregnancy and to better understand long term cardiovascular outcomes of treatment of mild chronic hypertension during pregnancy.


  1. Garovic VD, White WM, Vaughan L, et al. Incidence and long-term outcomes of hypertensive disorders of pregnancy. J Am Coll Cardiol 2020;75:2323-34.
  2. American College of Obstetricians and Gynecologists' Committee on Practice Bulletins—Obstetrics. ACOG Practice Bulletin No. 203: Chronic Hypertension in Pregnancy. Obstet Gynecol 2019;133:e26-50.
  3. Magee LA, von Dadelszen P, Rey E, et al. Less-tight versus tight control of hypertension in pregnancy. N Engl J Med 2015;372:407-17.
  4. SMFM Publications Committee. SMFM statement: benefit of antihypertensive therapy for mild-to-moderate chronic hypertension during pregnancy remains uncertain. Am J Obstet Gynecol 2015;213:3-4.
  5. Abalos E, Duley L, Steyn DW, Gialdini C. Antihypertensive drug therapy for mild to moderate hypertension during pregnancy. Cochrane Database Syst Rev 2018;10:CD002252
  6. Tita AT, Szychowski JM, Boggess K, et al. Treatment for mild chronic hypertension during pregnancy. N Engl J Med 2022;386:1781-92.
  7. Clinical Guidance for the Integration of the Findings of the Chronic Hypertension and Pregnancy (CHAP) Study ( 2022. Available at: Accessed 05/20/2022.

Clinical Topics: Congenital Heart Disease and Pediatric Cardiology, Prevention, CHD and Pediatrics and Prevention, CHD and Pediatrics and Quality Improvement, Hypertension

Keywords: ACC Annual Scientific Session, ACC22, Infant, Newborn, Pregnancy, Pregnancy Outcome, Antihypertensive Agents, Blood Pressure, Eclampsia, Birth Weight, Premature Birth, Gestational Age, Abruptio Placentae, Confidence Intervals, Control Groups, Goals, Maternal Health, Odds Ratio, Perinatal Death, Pregnant Women, Placenta, Treatment Outcome, Hypertension

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