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Evidence summaries

Antihypertensive Drug Therapy for Mild to Moderate Hypertension during Pregnancy

Antihypertensive drug therapy for mild to moderate hypertension during pregnancy reduces the risk of severe hypertension and pre-eclampsia. Antihypertensive drug therapy may reduce preterm birth without increase in the risk of small-for-gestational-age birth weight. Level of evidence: "A"

A Cochrane review [Abstract] 1 included 63 studies on women with mild to moderate hypertension (systolic blood pressure 140 to 169 mmHg and diastolic blood pressure 90 to 109 mmHg). From these, 58 studies (n=5 909 women) contributed data. Thirty-one trials compared an antihypertensive drug with placebo/no antihypertensive drug (3 485 women). Use of antihypertensive drugs halved the risk of severe hypertension. However, there was little evidence of a difference in the risk of pre-eclampsia, the risk of the baby dying, preterm birth, or small-for-gestational-age babies (table T1).

An antihypertensive drug versus placebo/no treatment

OutcomeRelative risk (RR)Participants (studies)
Severe hypertension0.49 (0.40 to 0.60)2 558 (20 studies)
Proteinuria/pre-eclampsia0.92 (0.75 to 1.14)2 851 (23 studies)
Baby dying*0.72 (0.50 to 1.04)3 365 (29 studies)
Preterm birth (<37 weeks)0.96 (0.83 to 1.12)2 141 (15 studies)
Small-for-gestational-age babies0.96 (0.78 to 1.18)2 686 (21 studies)
*Total reported fetal or neonatal death (including miscarriage)
In an open-label, multicenter trial 2, 2408 pregnant women with mild chronic hypertension were randomized to receive antihypertensive medications (active-treatment group) or no treatment unless severe hypertension (systolic pressure, ≥160 mm Hg; or diastolic pressure, ≥105 mm Hg) developed (control group). The primary-outcome event (composite of preeclampsia with severe features, medically indicated preterm birth at less than 35 weeks' gestation, placental abruption, or fetal or neonatal death) 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% 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 (aRR 1.04, 95% CI 0.82 to 1.31; P=0.76). The incidence of serious maternal complications was 2.1% and 2.8%, respectively (RR 0.75, 95% CI 0.45 to 1.26), and of severe neonatal complications 2.0% vs 2.6% (RR 0.77, 95% CI 0.45 to 1.30). The incidence of any preeclampsia in was 24.4% and 31.1%, respectively (RR 0.79, 95% CI 0.69 to 0.89), and of preterm birth was 27.5% and 31.4% (RR 0.87, 95% CI 0.77 to 0.99).