Treating Mild Chronic Hypertension Linked to Lower Risk of Adverse Pregnancy Outcomes

Alan T. Tita, MD, PhD

Treating mild chronic hypertension in pregnant women led to lower risk of adverse pregnancy outcomes than a strategy of reserving treatment unless hypertension became severe, according to recent findings.

The strategy of targeting blood pressure of ≥140/90 mm Hg was associated with better pregnancy outcomes without an increase in the risk of small-for-gestational-age birth weight, noted the study investigators.

“Our results suggest that the incidence of severe hypertension was lower among patients who received active treatment, which was consistent with the findings of previous trials and a systematic review of antihypertensive therapy for mild chronic hypertension in pregnancy,” wrote study author Alan T. Tita, MD, PhD, Department of Obstetrics and Gynecology, Center for Women’s Reproductive Health, Marnix E. Heersink School of Medicine, University of Alabama at Birmingham.

Previous data have reported antihypertensive treatment during pregnancy reduces the frequency of severe hypertension, but not data has shown improvements in maternal, fetal, or neonatal outcomes, leading to varying treatment recommendations, according to investigators.

The current multicenter, pragmatic, open-label, randomized trial, the Chronic Hypertension and Pregnancy (CHAP) project, was conducted at 70 recruiting sites in the United States. Eligibility criteria included pregnant women with known or new diagnosis of chronic hypertension and a viable singleton fetus before 23 weeks’ gestation.

Then, patients were randomized to a blood-pressure goal of 140/90 mm Hg (active treatment) or to standard (control) treatment, wherein no treatment was given unless severe hypertension developed (systolic pressure, ≥160 mm Hg; or diastolic pressure, ≥105 mm Hg).

A primary outcome was considered the composite of preeclampsia with severe features occurring up to 2 weeks after birth, medically indicated preterm birth before 35 weeks’ gestation, placental abruption, or fetal or neonatal death. Meanwhile, the safety outcome was small-for gestational-age birth weight below the 10th percentile for gestational age.

From September 2015 - March 2021, a total of 29,772 women underwent screening and 2149 women then were randomized at 61 locations. Investigators then noted a total of 83 patients were lost to follow-up, consisting of 38 (2.1%) in the active treatment group and 45 (3.8%) in the control group.

Data show a primary-outcome event occurred in 353 of 1170 patients (30.2%) in the active-treatment group and in 427 of 1155 (37.0%) in the control group (adjusted risk ratio, 0.82; 95% confidence interval [CI], 0.74 to 0.92; P <.001).

Moreover, investigators found preeclampsia with severe features happened in 272 patients (23.3%) in the active-treatment group and in 336 (29.1%) in the control group (adjusted risk ratio, 0.80; 95% CI, 0.70 - 0.92). They additionally saw medically indicated preterm birth before 35 weeks’ gestation occurred in 143 patients (12.2%) and in 193 (16.7%), respectively (adjusted risk ratio, 0.73; 95% CI, 0.60 - 0.89).

Data show 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; 95% CI, 0.82 - 1.31; P = .76).

Tita noted that further studies of the long-term effects of antihypertensive treatment on cardiovascular and other outcomes in this patient population may aid in clarifying the role of antihypertensive therapy.

The study, “Treatment for Mild Chronic Hypertension during Pregnancy,” was published in The New England Journal of Medicine.