BP Lowering in Pregnant Women Continues to Take Shape

SAN DIEGO — Standard practice has changed since a major trial revealed earlier this year that treating mild hypertension in pregnant women helps them without hurting their children. Nevertheless, questions about the particulars of this approach arose during a discussion at the annual Hypertension meeting hosted by the American Heart Association.

In April 2022, the CHAP trial showed good results treating mild hypertension in otherwise healthy pregnant women, who had a lower incidence of combined pre-eclampsia with severe features, medically indicated preterm birth at less than 35 weeks’ gestation, placental abruption, and fetal or neonatal death compared with the alternative — having antihypertensives withheld until they reached the blood pressure (BP) threshold of 160/105 mm Hg.

CHAP investigator Alan Tita, MD, PhD, of University of Alabama at Birmingham School of Medicine, said at the Hypertension meeting that longer-term studies are underway in the CHAP cohort, both for maternal and childhood outcomes.

For example, ongoing 5- to 10-year follow-up will provide information on how pregnant women fare after reaching the lactation phase depending on whether they stick to pregnancy-preferred medications or usual antihypertensives, he said, adding that future analysis will also probe the effect of any subsequent pregnancies during follow-up,

Even so, within a week of CHAP publication, the American College of Obstetricians and Gynecologists (ACOG) released clinical guidance — citing CHAP results — that lowered the threshold for initiation or titration of medical therapy for chronic hypertension in pregnancy down to 140/90 mmHg with no BP goal.

In contrast, subsequent interim guidance from the Society for Maternal-Fetal Medicine recommended a goal BP of <140/90 mmHg for pregnant people based on CHAP.

ACOG cautioned that acute, severe, or persistent BP elevations in the second half of pregnancy warrant further evaluation and a period of observation because of concern for superimposed pre-eclampsia. In CHAP, pre-eclampsia had to be excluded by clinical diagnostic work-up before any escalation of medication dose beyond 20 weeks of gestation.

Furthermore, third-trimester ultrasound assessment of fetal growth is still needed, according to ACOG, even though treatment of mild chronic hypertension in pregnant women did not increase the risk of fetal growth restriction in either CHAP or an older study, CHIPS.

The CHIPS trial had revealed stringent BP targets to be no help, albeit in a different population including both women with chronic hypertension and those with pregnancy-related hypertension such as gestational hypertension or pre-eclampsia.

Notably, CHAP study participants had been given labetalol or extended-release nifedipine as first-line BP medications, with no difference in results between these medications.

During a Hypertension Q&A, an attendee questioned whether it would be wiser for pregnant beta-blocker users to find an alternative, given this class of medication’s mixed safety data in this population.

An analysis scheduled for presentation in the late 2022 would suggest that patients do not need to switch medications, Tita responded.

Another question prompted him to clarify how BP was measured in the trial: “It’s a whole story behind measurement of BP in the CHAP trial,” he said. The start of the trial had clinicians using Omron devices across sites to measure BP according to best practices such as averaging multiple measurements and using periods of rest between reads, he explained.

“This was early on, and we quickly came to debate whether this is clinical practice. Does this really reflect what people do?” Tita said, explaining that the investigators later pivoted to allowing the usual devices of each participating facility while keeping standardized BP measurement processes.

He acknowledged that the impact of having different BP monitors in the trial, or “using what you would typically use in your setting,” will need to be evaluated further.