Antihypertensive Treatment during Pregnancy Linked to Better Outcomes, According to New NIH Study

Results from the largest trial to date examining chronic hypertension (CHTN) in pregnancy showed a strategy of targeting a blood pressure of <140/90 mm Hg was associated with better pregnancy outcomes than reserving treatment for severe HTN only.

Findings from the open-label, randomized Chronic Hypertension and Pregnancy (CHAP) trial, supported by the National Institutes of Health (NIH), were published simultaneously in the New England Journal of Medicine and presented at the American College of Cardiology’s 71st Scientific Sessions, held April 2-4, 2022.

“The impact of treating chronic hypertension during pregnancy represents a major step forward for supporting people at high risk for adverse pregnancy outcomes,” said principal investigator Alan Tita, MD, PhD, John C. Hauth Endowed Professor of Obstetrics and Gynecology, University of Alabama at Birmingham School of Medicine, in a NIH press release.

Antihypertensive treatment early in pregnancy could be significant for women who are at risk for preeclampsia or preterm births, but the benefits and safety of this approach are uncertain, according to the study abstract. Tita and colleagues aimed to determine whether a blood pressure treatment strategy during pregnancy to achieve targets that are recommended for non-pregnant adults (<120/80 mm Hg) is effective and safe.

Researchers assigned pregnant women with mild CHTN and singleton fetuses at a gestational age of <23 weeks to receive antihypertensive medications recommended for use in pregnancy (intervention arm) or to receive no such treatment unless severe HTN (systolic pressure, ≥160 mm Hg; or diastolic pressure, ≥105 mm Hg) developed (control arm).

The primary outcome was a composite of preeclampsia with severe features, medically indicated preterm birth at <35 weeks’ gestation, placental abruption, or fetal or neonatal death. Secondary outcomes included composites of serious neonatal or maternal complications, preeclampsia, and preterm birth, according to the abstract.

A total of 2408 women were enrolled in the trial at 61 US medical centers from 2015-2021 and were followed through delivery and for 6 weeks thereafter. There were 1208 participants in the intervention arm and 1200 in the control group.

Investigators found that the incidence of a primary-outcome event was lower in the intervention arm than in the control arm (30.2% vs 37%; adjusted risk ratio [aRR], 0.82; 95% confidence interval [CI], 0.74-0.92; P<.001).

The incidence of serious maternal complications among the intervention arm and control group was 2.1% and 2.8%, respectively (RR, 0.75; 95% CI, 0.45-1.26), and the incidence of severe neonatal complications was 2% and 2.6%, respectively (RR, 0.77; 95% CI, 0.45-1.30). Also, the incidence of any preeclampsia was 24.4% and 31.1%, respectively (RR, 0.79; 95% CI, 0.69-0.89), and the incidence of preterm birth was 27.5% and 31.4% (RR, 0.87; 95% CI, 0.77-0.99).

In addition, antihypertensive treatment was not associated with an increased risk of small-for-gestational-age birth weight. Approximately 11.2% of infants born to participants in the intervention arm and 10.4% of babies born to those in the control group had impaired fetal growth, defined for the purpose of the study as birth weights below the 10th percentile.

Future studies analyzing long-term health outcomes of participants and their children are needed, the team noted, to further clarify the use of HTN treatments during pregnancy.

Reference: Tita AT, Szychowski JM, Boggess K, et al. Treatment for mild chronic hypertension during pregnancy. N Engl J Med. Published online ahead of print April 2, 2022.