New data on hypertension control during pregnancy: CHAP Trial

It is well-established that maternal hypertension is linked to adverse pregnancy outcomes. However, the question of whether to treat chronic mild hypertension during pregnancy has been a controversy for decades because earlier trials suggested possible fetal growth restriction in women with treatment-induced blood pressure reduction. Now we have so much awaited data from a large, open-label, randomized trial demonstrating that pregnant women with even mild hypertension should receive blood pressure–lowering medications to reduce the likelihood of adverse outcomes for the mother and the child. The Chronic Hypertension and Pregnancy (CHAP) trial results were reported at the annual scientific sessions of the American College of Cardiology and simultaneously published in the New England Journal of Medicine.

In this open-label, multicenter, randomized trial, pregnant women with mild chronic hypertension defined as a blood pressure of >140/90 mm Hg and singleton fetuses at a gestational age of less than 23 weeks were randomly assigned to receive antihypertensive medications recommended for use in pregnancy (active-treatment group) or to receive no such treatment unless severe hypertension (systolic pressure, ≥160 mm Hg; or diastolic pressure, ≥105 mm Hg) developed (control group). Target blood pressure in the intervention group was less than 140/90 mm Hg. The beta-blocker labetalol or the calcium channel blocker nifedipine as single agents were the preferred antihypertensive medications in the protocol, but other medications such as amlodipine or methyldopa were also permitted. To reach the blood pressure goal, the single-agent therapy was titrated to the maximum dose before starting a second agent. The primary outcome was a composite of preeclampsia with severe features, medically indicated preterm birth at less than 35 weeks’ gestation, placental abruption, or fetal or neonatal death. The safety outcome was small-for-gestational-age birth weight below the 10th percentile for gestational age. Secondary outcomes included composites of serious neonatal or maternal complications, preeclampsia, and preterm birth.

A total of 2408 women were enrolled in the trial. The incidence of a primary-outcome event was lower in the active-treatment group than in the control group (30.2% vs. 37.0%), for an adjusted risk ratio of 0.82 (95% confidence interval [CI], 0.74 to 0.92; P<0.001). The percentage of small-for-gestational-age birth weights below the 10th percentile was 11.2% in the active-treatment group and 10.4% in the control group (adjusted risk ratio, 1.04; 0.82 to 1.31; P=0.76). The incidence of serious maternal complications was 2.1% and 2.8%, respectively (risk ratio, 0.75; 95% CI, 0.45 to 1.26), and the incidence of severe neonatal complications was 2.0% and 2.6% (risk ratio, 0.77; 95% CI, 0.45 to 1.30). The incidence of any preeclampsia in the two groups was 24.4% and 31.1%, respectively (risk ratio, 0.79; 95% CI, 0.69 to 0.89), and the incidence of preterm birth was 27.5% and 31.4% (risk ratio, 0.87; 95% CI, 0.77 to 0.99).


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