ACC 2022: Pregnant Women With Mild Hypertension Benefit From Antihypertensive Therapy
Treatment was associated with reduced risk of severe preeclampsia and preterm birth
April 2, 2022—Washington, DC—Among women with chronic mild hypertension during pregnancy, using antihypertensive therapy to reduce blood pressure to below 140/90 mm Hg reduced the risk of adverse pregnancy outcomes, according to research presented at the American College of Cardiology 2022 Scientific Sessions, which took place here and online from April 2 to 4.
“Chronic hypertension affects upwards of 2% of pregnancies in the United States,” said lead author Alan Tita, MD, PhD, of the University of Alabama at Birmingham Heersink School of Medicine, during his presentation of the data. “It is rising due to older age at childbirth and obesity. Blacks are disproportionately affected. Chronic hypertension causes several maternal and fetal complications, including death, preeclampsia, … babies that are small for gestational age (SGA) based on their birth weight, preterm birth, and cardiovascular morbidities. The American College of Obstetricians and Gynecologists classifies chronic hypertension in pregnancy into two groups: severe, with blood pressures of at least 160/110 mm Hg, and mild or non-severe, with blood pressures below that threshold.” He noted, however, that this definition of non-severe disease encompasses ACC/American Heart Association stage 2 hypertension. The risks and benefits of antihypertensive therapy among pregnant patients remain unclear.
For the open-label, multicenter CHAP trial, 2404 women with mild chronic hypertension and a singleton pregnancy < 23 weeks’ gestation were randomized, stratified by center, to either treatment with a first-line antihypertensive for pregnancy to a blood pressure goal < 140/90 mm Hg (n = 1208) or to no treatment unless blood pressure was ≥ 160/105 mm Hg (n = 1200). The main antihypertensive agents used were labetalol or nifedipine ER. Others (methyldopa, amlodipine) were accepted, but these were not provided through the study.
The centrally adjudicated primary outcome was a composite of preeclampsia with severe features, preterm birth < 35 weeks, abruption, and neonatal/fetal death. The safety outcome was SGA (birth weight < 10th percentile). Secondary outcomes included preterm birth (< 37 weeks) and preeclampsia. Patients were followed up through 6 weeks postpartum.
The two groups of patients were similar at baseline. At enrollment, 56% were on antihypertensives. Overall, 48% were black, 28% were white non-Hispanic, and 20% were Hispanic. In addition, 16% were diabetic, and their mean body mass index was 37.6 kg/m2.
The primary outcome incidence was lower in the treatment group, at 30.2% versus 37.0%, for a relative risk of 0.82 (95% confidence interval 0.74–0.92, P < .001). Also lower with active therapy were the incidence of severe preeclampsia (23.3% vs 29.1%, relative risk 0.80, 95% confidence interval 0.70–0.92) and indicated preterm birth < 35 weeks (12.2% vs 16.7%, relative risk 0.73, 95% confidence interval 0.60–0.89). The number needed to treat to prevent one of these events was 14.7. There were no significant differences between the two groups with respect to abruption or fetal/neonatal death, nor were there notable differences observed in subgroup analyses.
The safety outcome was similar for both groups, at 11.2% versus 10.4%, P = .76.
A composite maternal morbidity outcome that included death, heart failure, stroke, myocardial infarction/angina, pulmonary edema, intensive care unit admission, encephalopathy, and acute kidney injury was similar for both groups. However, rates of any preeclampsia (24.4% vs 31.1%), worsening chronic hypertension (10.9% vs 13.0%), and severe hypertension (36.1% vs 44.3%) were all lower in the intervention arm.
Rates of multiple neonatal outcomes, evaluated as a composite and individually, did not differ between the two groups, with the exception of preterm birth (27.5% vs 31.4%) and low birthweight < 2500 g (19.2% vs 23.1%), which were lower in the intervention arm.
“CHAP supports treatment of chronic hypertension in pregnancy to a blood pressure goal of < 140/90 mm Hg, especially continuing established antihypertensive therapy,” concluded Dr. Tita. “Long-term studies will further clarify these treatment effects.”
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