Treatment of mild chronic hypertension in pregnant women has reduced the risk of adverse pregnancy outcomes compared to a strategy of withholding treatment unless hypertension becomes severe, recent findings show.

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

“Our results suggest that the incidence of severe hypertension was lower in patients who received active treatment, which was consistent with results from previous trials and a systematic review of antihypertensive therapy for mild chronic hypertension during 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 reported that antihypertensive treatment during pregnancy reduced the frequency of severe hypertension, but no data showed improved maternal, fetal or neonatal outcomes, leading to variable treatment recommendations, researchers say. .

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 a known or new diagnosis of chronic hypertension and a single viable fetus before 23 weeks gestation.

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

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 to March 2021, a total of 29,772 women were screened and 2,149 women were subsequently randomized to 61 sites. Investigators then noted that a total of 83 patients were lost to follow-up, including 38 (2.1%) in the active treatment group and 45 (3.8%) in the control group.

Data show that 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 (risk adjusted relative, 0.82, 95% confidence interval [CI], 0.74 to 0.92; P<.001>

Additionally, investigators found preeclampsia with severe features in 272 patients (23.3%) in the active treatment group and 336 (29.1%) in the control group (adjusted risk ratio, 0.80; 95% CI, 0.70 – 0.92). They further saw medically indicated preterm delivery before 35 weeks gestation in 143 (12.2%) and 193 (16.7%) patients, respectively (adjusted relative risk, 0.73; 95% CI, 0 .60 – 0.89).

The data show that 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 relative risk, 1 .04; 95% CI, 0.82 – 1.31; P = 0.76).

Tita noted that further studies of the long-term effects of antihypertensive therapy on cardiovascular and other outcomes in this patient population could help clarify the role of antihypertensive therapy.

The study, “Treatment of mild chronic hypertension in pregnancy,” was published in The New England Journal of Medicine.