Chronic Hypertension and Pregnancy - CHAP

May 12, 2022
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Author/Summarized by Author:
Anthony A. Bavry, MD, MPH, FACC
Summary Reviewer:
Deepak L. Bhatt, MD, MPH, MBA, FACC
Trial Sponsor:
National Heart, Lung, and Blood Institute
Date Presented:
04/02/2022
Date Published:
04/02/2022
Original Posted Date:
05/12/2022
References

Contribution To Literature:

The CHAP trial showed that antihypertensive therapy improves pregnancy outcomes among pregnant women with mild chronic hypertension.

Description:

The goal of the trial was to evaluate antihypertensive therapy compared with control among pregnant women with mild chronic hypertension.

Study Design

  • Randomized
  • Parallel
  • Open-label

Pregnant individuals with mild chronic hypertension were randomized to a blood pressure goal <140/90 mm Hg (active treatment) (n = 1,208) versus control (n = 1,200). In the control group, antihypertensive therapy was withheld unless the blood pressure was ≥160/105 mm Hg.

In the active treatment group, patients received standard first-line antihypertensive agents in pregnancy (labetalol or extended-release nifedipine); however, amlodipine or methyldopa could also be used, if needed. The medication was titrated to the maximum dose, as necessary, before starting a second agent.

  • Total number of enrollees: 2,408
  • Duration of follow-up: 34 weeks
  • Mean patient age: 32 years
  • Percentage with diabetes: 15.8%

Inclusion criteria:

  • Pregnant women with mild chronic hypertension
  • Known chronic hypertension was confirmed by elevated blood pressure and previous/current antihypertensive therapy, while new chronic hypertension was defined as systolic blood pressure ≥140 mm Hg or diastolic blood pressure ≥90 on ≥2 occasions ≥4 hours apart
  • Gestational age <23 weeks

Exclusion criteria:

  • Need for >1 antihypertensive medication, secondary hypertension, multiple fetuses, high-risk illnesses, or complications that could warrant treatment at a lower blood pressure level
  • Obstetric conditions that increase fetal risk
  • Contraindications to first-line antihypertensive drugs in pregnancy

Other salient features/characteristics:

  • Non-Hispanic black women: 48%
  • Mean body mass index: 37.5 kg/m2
  • Mean systolic blood pressure between randomization and delivery: 129.5 mm Hg in the active treatment group vs. 132.6 mm Hg in the control group

Principal Findings:

The primary outcome, composite of pre-eclampsia with severe features, medically indicated preterm birth at <35 weeks’ gestation, placental abruption, or fetal/neonatal death, occurred in 30.2% of the active treatment group vs. 37.0% of the control group (p < 0.001).

Secondary outcomes:

  • The safety outcome, small-for-gestational-age birth weight below the 10th percentile for gestational age: 11.2% in the active treatment group vs. 10.4% in the control group (p = 0.56)
  • Pre-eclampsia with severe features: 23.3% in the active treatment group vs. 29.1% in the control group
  • Fatal/neonatal death: 3.5% in the active treatment group vs. 4.3% in the control group

Interpretation:

Among pregnant women with mild chronic hypertension, antihypertensive therapy targeted to a blood pressure <140/90 mm Hg reduced the incidence of adverse pregnancy outcomes compared with usual care. Active treatment improved outcomes without increasing the risk for low birth weight. A large proportion of non-Hispanic blacks were enrolled in this trial.

References:

Tita AT, Szychowski JM, Boggess K, et al., on behalf of the Chronic Hypertension and Pregnancy (CHAP) Trial Consortium. Treatment for Mild Chronic Hypertension During Pregnancy. N Engl J Med 2022;386:1781-92.

Editorial: Greene MF, Williams WW. Treating Hypertension in Pregnancy. N Engl J Med 2022;386:1846-7.

Presented by Dr. Alan Tita at the American College of Cardiology Annual Scientific Session (ACC 2022), Washington, DC, April 2, 2022.

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

Keywords: Abruptio Placentae, ACC22, ACC Annual Scientific Session, Amlodipine, Antihypertensive Agents, Blood Pressure, Gestational Age, Hypertension, Infant, Infant, Low Birth Weight, Infant, Newborn, Labetalol, Methyldopa, Nifedipine, Perinatal Death, Placenta, Pre-Eclampsia, Pregnancy, Pregnancy Outcome, Pregnant Women, Premature Birth, Primary Prevention, Women


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