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Evevident
Original paper
2022NEJMOB/GYN

CHAP

Treatment for Mild Chronic Hypertension during Pregnancy

RCTObstetrics / hypertension

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Overview

Treating mild chronic hypertension in pregnancy to <140/90 improved pregnancy outcomes without increasing small-for-gestational-age births.

Clinical takeaway

CHAP changed the threshold for treating mild chronic hypertension in pregnancy, supporting active treatment rather than waiting for severe-range pressures.

Key result

Primary composite outcome was 30.2% with active treatment vs 37.0% with control (adjusted RR 0.82).

Practice impact

Treat chronic HTN in pregnancy at 140/90 rather than waiting for severe range, using pregnancy-compatible agents.

Evidence

Study design

Open-label, multicenter randomized controlled trial.

Enrollment

2,408

Follow-up

Through pregnancy and delivery.

Geography

United States

Clinical question

Does treatment of mild chronic hypertension in pregnancy improve maternal/fetal outcomes without impairing fetal growth?

Population

  • Pregnant patients with mild chronic hypertension and singleton gestation before 23 weeks.

Intervention

Active antihypertensive treatment targeting BP <140/90 mm Hg (commonly labetalol or extended-release nifedipine).

Comparator

No treatment unless severe hypertension (>=160/105 mm Hg) developed.

Primary outcome

Composite of preeclampsia with severe features, medically indicated preterm birth <35 weeks, placental abruption, or fetal/neonatal death.

Treating mild chronic hypertension to below 140/90 mm Hg improved pregnancy outcomes without increasing small-for-gestational-age births.

Adjusted risk ratio / 0.82 / CI 95% CI 0.74-0.92 / p=<0.001

Key results

  • Primary composite outcome: 30.2% with active treatment vs 37.0% with control; adjusted risk ratio 0.82 (95% CI 0.74-0.92; p<0.001).
  • Small-for-gestational-age birth weight below the 10th percentile was not increased (11.2% vs 10.4%).
  • Reductions in severe preeclampsia and medically indicated preterm birth drove the benefit.

Harms

  • Small-for-gestational-age birth weight (a prior concern with BP lowering) was not increased.
  • No safety signal favored the non-treatment strategy.

Clinical Use

When to cite

  • When treating mild chronic hypertension in pregnancy rather than waiting for severe-range blood pressures.

Practice impact

  • Treat chronic HTN in pregnancy at 140/90 rather than waiting for severe range, using pregnancy-compatible agents.

Applicability

  • Most applicable to pregnant patients with mild chronic hypertension and a singleton gestation before 23 weeks.

Limitations

  • Open-label pragmatic design (though outcomes were adjudicated).
  • Medication choice was individualized among common pregnancy-compatible options.
  • Predominantly enrolled patients already on or eligible for oral therapy.

Common misinterpretations

  • The 140/90 mm Hg threshold replaces the older practice of withholding treatment until the severe range.
  • ACE inhibitors and ARBs remain contraindicated in pregnancy; CHAP used agents such as labetalol and nifedipine.

Citation

Tita AT, Szychowski JM, Boggess K, et al. Treatment for Mild Chronic Hypertension during Pregnancy. N Engl J Med. 2022;386(19):1781-1792. doi:10.1056/NEJMoa2201295

In pregnant women with mild chronic hypertension, a strategy of targeting a blood pressure of less than 140/90 mm Hg was associated with better pregnancy outcomes than a strategy of reserving treatment only for severe hypertension, with no increase in the risk of small-for-gestational-age birth weight.