Treating mild chronic hypertension associated with better pregnancy outcome

1. Treatment of mild chronic hypertension in pregnant women was associated with lower risks of adverse pregnancy outcomes.

2. Treating mild chronic hypertension was not correlated with compromised fetal growth.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Chronic hypertension is common in pregnancies. It disproportionately affects Black women and is associated with an increased risk of adverse outcomes including preeclampsia, prematurity, placental abruption, and neonatal death. Although consensus exists for treating severe hypertension during pregnancy (blood pressure [BP]>160/110mmHg), antihypertensive therapy for mild hypertension (BP<160/110mmHg) has been controversial due to its association with small-for-gestational-age birth weight. The current study sought to investigate the benefits and safety of treating mild chronic hypertension (BP<160/110mmHg) with antihypertensives in singleton-pregnant women with a BP target of less than 140/90mmHg, compared to a control of withholding therapy until BP reached 160/105mmHg (the conservative threshold for severe hypertension). The results showed that treating mild chronic hypertension was linked to lower adverse pregnancy outcomes than in the control group. Furthermore, the was no increase in the incidence of small-for-gestational-age birth weight in the treatment group. This study provided evidence for the benefits and safety of pharmacologic therapy for mild hypertension during pregnancy, supporting its recommendation.

Click here to read the study in NEJM

Relevant Reading: Antihypertensive drug therapy for mild to moderate hypertension during pregnancy

In-Depth [randomized controlled trial]: This open-label, multicenter, randomized trial assessed the benefits and safety of initiating antihypertensive therapy in pregnant women with mild chronic hypertension. Participants were included if they were pregnant with singleton fetuses at a gestational age of fewer than 23 weeks and had mild chronic hypertension. BP threshold for randomization was 140 to 159mmHg systolic, 90 to 104mmHg diastolic, or both, depending on whether the patient was on an antihypertensive regimen. Exclusion criteria included severe hypertension requiring more than one medication, secondary hypertension, multiple fetuses, high-risk conditions warranting treatment at a lower BP, and contraindications to the recommended drugs. In total, 2408 women were enrolled and randomized to the treatment group, who were initiated on antihypertensive medications to target BP of less than 140/90mmHg; and the control group, for whom therapy was only started when BP was greater than 160/105mmHg. The primary outcome was a composite of preeclampsia with severe features, medically necessary preterm birth at less than 35 weeks gestation, placental abruption, or neonatal death. The safety outcome was small-for-gestational-age birthweight below the 10^th percentile. Secondary outcomes included composites of maternal death or serious complications, serious neonatal complications, any preterm births, and preeclampsia. Overall, the incidence of the primary outcome was lower in the treatment group (30.2%) than in the control group (37.0%), with an adjusted risk ratio (RR) of 0.82 (95% confidence interval [CI], 0.74-0.92, P<0.001). The percentage of small-for-gestational-age birthweights was 11.2% in the treatment group and 10.4% in the control group (adjusted RR, 1.04; 95% CI, 0.82-1.31), indicating no significant differences. The incidence of serious maternal complications was 2.1% and 2.8% for the treatment and control groups, respectively (RR, 0.75; 95% CI, 0.45-1.26); while the incidence of severe neonatal complications was 2.0% and 2.6%, respectively (RR, 0.77; 95% CI, 0.45-1.30). The incidence of preterm birth was 27.5% and 31.4%, respectively (RR, 0.87; 95% CI, 0.77-0.99); and the incidence of preeclampsia was 24.4% and 31.1%, respectively (RR, 0.79; 95% CI, 0.69-0.89). The study population’s ethnic and racial composition mirrored that of the general population who have hypertension during pregnancy. Therefore, the results of this study provided evidence for the benefits and safety to support active antihypertensive therapy for mild chronic hypertension in pregnant women.

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