Treating mild chronic hypertension in pregnancy appears beneficial, safe for mother and baby
Click Here to Manage Email Alerts
WASHINGTON — Treating mild chronic hypertension during pregnancy to a BP goal of less than 140/90 mm Hg reduced adverse pregnancy outcomes and did not impair fetal growth, according to a new study.
Pregnant women with mild chronic hypertension who received antihypertensive medication had significantly reduced rates of severe preeclampsia, preterm birth before 35 weeks’ gestation, placental abruption and fetal or neonatal death compared with a strategy of reserving treatment only for women who developed severe hypertension during pregnancy.
Further, there was no increase in risk for small-for-gestational-age birth weight when the active treatment strategy was followed, Alan T. Tita, MD, PhD, director of the Center for Women’s Reproductive Health and professor of obstetrics and gynecology at University of Alabama at Birmingham Heersink School of Medicine, said during a late-breaking clinical trial presentation at the American College of Cardiology Scientific Session.
“Currently, antihypertensive therapies are recommended for the general, nonpregnant population; however, the benefits and safety in pregnancy are uncertain. We are therefore faced with a situation in which there is a conflict in recommendations for this population and also, importantly, an international controversy regarding whether to treat [pregnant women] with non-severe hypertension,” Tita said.
Evaluating treatment of mild hypertension
The Chronic Hypertension and Pregnancy (CHAP) Trial Consortium aimed to evaluate whether it is beneficial and safe to prescribe BP medication to pregnant women with mild chronic hypertension, defined as BP less than 160/100 mm Hg. The study, led by researchers at the University of Alabama at Birmingham and funded by the NHLBI, enrolled 2,408 pregnant women with singleton fetuses who were less than 23 weeks into their pregnancy at 61 sites from 2015 to 2021. Women were randomly assigned to receive first-line antihypertensive medications recommended for use in pregnancy with a target BP of less than 140/90 mm Hg or no treatment unless severe hypertension developed. Severe hypertension was defined as 160/105 mm Hg or higher.
More than half (56%) of women were already receiving antihypertensive medication at baseline. Women in the active treatment group were prescribed labetalol or nifedipine, or other medications such as amlodipine or methyldopa based on patient preference. Labetalol (61.7%) and nifedipine (35.6%) were most frequently used.
Maternal and fetal outcomes
Women who received antihypertensive medication during pregnancy had a reduced incidence of the primary outcome — a composite of severe preeclampsia, preterm birth before 35 weeks, placental abruption and fetal or neonatal death — which occurred in 30.2% of the active treatment group compared with 37% of the control group (adjusted risk ratio = 0.82; 95% CI, 0.74-0.92; P < .001). The number needed to treat to prevent one of these outcomes was 14.7, Tita said.
For the primary safety outcome — small-for-gestational-age birth weight below the 10th percentile for gestational age — the incidence was 11.2% in the active treatment group compared with 10.4% in the control group (adjusted risk ratio = 1.04; 95% CI, 0.82-1.31; P = .76).
In other results, the incidence of serious maternal complications was 2.1% in the active treatment group vs. 2.8% in the control group (RR = 0.77; 95% CI, 0.45-1.3), any preeclampsia was 24.4% vs. 31.1%, respectively (RR = 0.79; 95% CI, 0.69-0.89) and preterm birth was 27.5% vs. 31.4%, respectively (RR = 0.87; 95% CI, 0.77-0.99). Maternal death was similar and rare overall. In general, maternal CV outcomes appeared more favorable, although not significantly better, among women whose hypertension was treated, especially for maternal death, pulmonary edema, kidney failure and ICU admissions. The same was true for severe neonatal complications, according to an ACC press release.
The results were simultaneously published in The New England Journal of Medicine.
‘Practice-changing’ results
It is estimated that 2% of U.S. women enter pregnancy with high BP. Of those, up to 80% have mild chronic hypertension. Rates are rising due to older age at childbirth and obesity, and Black women are disproportionately affected, Tita said.
The study population “mirrored the age and racial and ethnic diversity of women with chronic hypertension who are giving birth in the United States,” the researchers wrote in NEJM.
Nearly half (48%) of the women were characterized as non-Hispanic Black, 28% non-Hispanic white and 20% Hispanic. Sixteen percent had diabetes and the mean BMI was 37.6 kg/m2.
In a discussion following the presentation, Athena Poppas, MD, FACC, director of the Lifespan Cardiovascular Institute in Providence, Rhode Island, said that this is “a fantastic study — very well run and really practice-changing,” noting that a trial like this is “not easy to do.”
“One of the reasons we don’t have as much data in pregnant patients is some of the logistical and ethnic concerns we’ve had. This should certainly alter our practice,” Poppas, who is also chief of cardiology and professor of medicine at the Warren Alpert School of Medicine at Brown University and immediate past president of the ACC, said.
“We conclude that CHAP supports treatment of [mild chronic hypertension] to a BP goal less than 140/90 mm Hg in pregnancy, especially continuation of established antihypertensive therapy. Longer-term studies will further clarify the treatment effect, including maternal and childhood outcomes,” Tita said.
The CHAP Trial Consortium was recently awarded a grant from the NHLBI to follow the women in the study for up to 10 years and also proposed a study to follow the babies of these women, according to the release.
Reference:
- Tita AT, et al. N Engl J Med. 2022;doi:10.1056/NEJMoa2201295.
- Treating milder forms of pre-existing high blood pressure during pregnancy improves some outcomes. https://www.acc.org/About-ACC/Press-Releases/2022/04/02/12/40/Treating-Milder-Forms-of-Pre-Existing-High-Blood-Pressure-During-Pregnancy. Published April 2, 2022. Accessed April 2, 2022.
Perspective
Back to Top
Janet Wei, MD, FACC
We have had significant confusion regarding BP threshold for treatment of pregnant women with mild chronic hypertension, mainly due to the concern of fetal risk. Guidelines agree to treat BP >1 40/90 mm Hg when there is superimposed preeclampsia, and the CHIPS trial demonstrated that more aggressive BP control prevented the development of severe hypertension but not preeclampsia. Other observational studies have also shown that lower BP levels during pregnancy have been associated with lower incidences of superimposed preeclampsia and preterm delivery, including in Black women. The 2019 American College of Obstetricians and Gynecologists’ (ACOG) practice bulletin on chronic hypertension in pregnancy stated that it is reasonable to continue to manage a chronic hypertensive patient in pregnancy similar to the ACC/American Heart Association guidelines for chronic hypertension, but the thresholds are not well defined.
CHAP found that treating mild chronic hypertension in pregnancy to a goal of < 140/90 mm Hg decreased risk for preeclampsia with severe features and preterm birth compared to a goal of < 160/105 mm Hg, with no increase in the risk for small-for-gestational-age birth weight. Furthermore, there was no increased risk of severe neonatal complications. This is an important trial that will change clinical practice and improve maternal outcomes.
We need to understand the long-term effect of antihypertensive treatment on CV outcomes in pregnant women with hypertensive disorders of pregnancy and their offspring.
Although aspirin did not appear to influence the treatment effect in CHAP, less than half of the patients were taking aspirin by 23 weeks of gestation. ACOG recommends women with chronic hypertension to be initiated on aspirin for preeclampsia prevention optimally before 16 weeks’ gestation. Thus, it is possible that the combination of aspirin therapy and BP control < 140/90 mm Hg may have a greater effect on prevention of preeclampsia in pregnant women with mild chronic hypertension.
The difference in outcomes was seen despite a relatively small difference (~3 mm Hg for systolic BP and ~2 mm Hg for diastolic BP) in the overall achieved mean BPs between the active treatment group and control group. However, there appeared to be larger differences in BP over time.
Perspective
Back to Top
Mary Norine Walsh, MD, MACC
I think the data are very reassuring and should make not just cardiologists but all primary care clinicians including OB/GYN, family medicine and others who see pregnant women who have the hypertension described in the CHAP trial much more at ease with regard to the treating goal. They may even choose to use the two drugs that were provided to the patients in the trial, because this is the first time there has been any sort of guidance for those patients. It is important that [the findings are] reassuring, as it has always been a worry about babies being small for gestational age if we overtreat. This is really a landmark move forward in treating pregnant patients.
Collapse
Tita A, et al. Joint American College of Cardiology/Journal of the American College of Cardiology Late-Breaking Clinical Trials. Presented at: American College of Cardiology Scientific Session; April 2-4, 2022; Washington, D.C. (hybrid meeting).
Read more about
Click Here to Manage Email Alerts