Control of Hypertension in Pregnancy Study | Clinical Trial - CHIPS


The benefit of tight blood pressure control during pregnancy in hypertensive patients is unknown. The current trial sought to study the merits of tight versus less-intensive blood pressure control in hypertensive pregnant patients.

Contribution to the Literature: The CHIPS trial showed that less-intensive blood pressure control during pregnancy may not be better than tighter control; the latter may reduce the incidence of severe hypertension during pregnancy.

Study Design

A total of 1,030 patients were randomized, 519 to less-tight control and 511 to tight control. Baseline characteristics were fairly similar between the two arms. The median age at expected date of delivery was 34 years, with a median time of enrollment of 24 weeks of gestation. Nearly three quarters of the patients had pre-existing hypertension, and 58% were on antihypertensive medication at enrollment. About 6% had coexisting gestational diabetes mellitus. Median duration of study participation was 12 weeks.

Eligible women were randomly assigned in a 1:1 ratio to less-tight control (target diastolic blood pressure 100 mm Hg) or tight control (target diastolic blood pressure 85 mm Hg) until delivery. The study protocol recommended labetalol as the drug of first choice. Angiotensin-converting enzyme (ACE) inhibitors, angiotensin-receptor antagonists, direct renin inhibitors, and atenolol were not permitted before delivery.

Inclusion criteria:

  • Nonsevere nonproteinuric pre-existing hypertension or gestational hypertension
  • Diastolic blood pressure of 90-105 mm Hg if they were not receiving antihypertensive therapy, or 85-105 mm Hg if they were receiving such treatment
  • Live singleton fetus at 14 weeks 0 days, to 33 weeks 6 days of gestation
  • Total number of enrollees: 1,030
  • Duration of follow-up: 12 weeks
  • Mean patient age: 34 years
  • Percentage female: 100%

Exclusion criteria:

  • Systolic blood pressure of 160 mm Hg or higher
  • Proteinuria
  • An ACE inhibitor at 14 weeks 0 days of gestation or later
  • Contraindication to either trial group because of a pre-existing condition (e.g., pregestational diabetes or renal disease) or needed to be delivered for maternal or fetal reasons
  • Known multiple gestation or a fetus with a major anomaly or chromosomal abnormality
  • Plans to terminate the pregnancy
  • Previously participated in CHIPS

Principal Findings:

The primary outcome, pregnancy loss or high-level neonatal care for >48 hours, was similar between the less-intensive and tight control arms (31.4% vs. 30.7%, hazard ratio 1.02, 95% confidence interval 0.77-1.35). Individual components including miscarriage (0 vs. 0.2%), perinatal death (2.8% vs. 2.3%), and need for high-level neonatal care >48 hours (29.4% vs. 29.0%) were similar between the two arms. Other perinatal endpoints were also similar. The frequency of severe hypertension was higher in the less-tight control arm (40.6% vs. 27.5%, p < 0.0001). Pre-eclampsia rates were similar (48.9% vs. 45.7%). There was one maternal stroke in the tight control arm, and none in the less-tight control arm.


The results of the CHIPS trial indicate that less-tight control of blood pressure of maternal hypertension (both pre-existing and gestational) during pregnancy is not superior to tighter control, with similar maternal and perinatal outcomes. The incidence of severe hypertension, but not pre-eclampsia, was lower with tighter control. These are important findings and suggest that a tighter blood pressure control in select patients may be the favored approach.


Magee LA, von Dadelszen P, Rey E, et al. Less-Tight Versus Tight Control of Hypertension in Pregnancy. N Engl J Med 2015;372:407-417.

Clinical Topics: Congenital Heart Disease and Pediatric Cardiology, Diabetes and Cardiometabolic Disease, Prevention, Vascular Medicine, CHD and Pediatrics and Prevention, Hypertension

Keywords: Blood Pressure, Blood Pressure Determination, Diabetes, Gestational, Hypertension, Hypertension, Pregnancy-Induced, Pre-Eclampsia, Pregnancy, Labetalol, Proteinuria, Antihypertensive Agents, Fetus

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