Skip to main content

Kim Boggess, MD, is the co-author of a New England Journal of Medicine paper detailing important maternal and fetal health findings as part of the largest-ever clinical trial on hypertension during pregnancy.

More than 2 percent of pregnant women in the United States have chronic hypertension, or high blood pressure. Medical professionals agree that severe chronic hypertension during pregnancy should be treated with medications. Treating non-severe or mild forms of chronic hypertension during pregnancy, however, has led to a divide in medical recommendations for decades.

But a new study published today in the New England Journal of Medicine provides evidence that treating mild chronic hypertension with medications is beneficial and safe for the mom and baby. The findings provide for the first time comprehensive, evidence-based data for treating non-severe forms of chronic hypertension during pregnancy.

The results are from the Chronic Hypertension and Pregnancy trial, or CHAP, consortium of more than 60 clinical sites across the United States that was led by the University of Alabama at Birmingham. The trial evaluated the effects of prescribing blood pressure medication to pregnant women with mild chronic hypertension. The study results showed this treatment improved pregnancy outcomes without compromising the baby’s growth and overall health, which has been a primary concern from physicians for years.

“This research will likely change clinical care for pregnant patients with hypertension,” said Kim Boggess, MD, professor in the Department of Obstetrics and Gynecology and principal investigator at the UNC Medical Center site for this study. “The findings from this largest-ever clinical trial of hypertension during pregnancy will improve health of mothers and babies around the world.”

Chronic hypertension causes serious and life-threatening complications for pregnant women and their babies. Between 70 and 80 percent of pregnant women with chronic hypertension fall into the ‘mild’ category where there is not a medical consensus for treatment.

“In light of these new data, it is important that we reevaluate current recommendations, update practice guidelines and begin treating most — if not all — pregnant women with chronic hypertension with medication,” said Alan Tita, MD, PhD, professor of obstetrics and gynecology in the UAB Marnix E. Heersink School of Medicine, principal investigator for the CHAP trial, and lead author of the NEJM paper.

Chronic hypertension increases the risk for pregnancy complications, including maternal and perinatal death. The condition is associated with a three- to five-times increased risk for preeclampsia, placental abruption, preterm birth, small for gestational age newborns and perinatal death. It is also associated with a five- to 10-times increased risk for maternal death, heart failure, stroke, pulmonary edema and acute kidney injury.

The CHAP consortium — with clinical and data coordinating centers in the UAB departments of Obstetrics and Gynecology and Center for Women’s Reproductive Health in the Heersink School of Medicine and the department of Biostatistics in the School of Public Healthlaunched the CHAP program in 2014 with funding from the National Institutes of Health’s Heart, Lung and Blood Institute. From September 2015 to March 2021, CHAP enrolled more than 2,400 pregnant women with known mild chronic hypertension, whose blood pressure was greater than 140/90 mmHg but less than 160/105 mmHg.

Notably, the CHAP trial is one of the most comprehensive and diverse studies of its kind. The Black patient population is disproportionately affected by chronic hypertension, and almost 50 percent of study participants were Black mothers.

Trial parameters, results

Participants were randomized into active and standard treatment groups. The active group was prescribed blood pressure medication, mostly labetalol or nifedipine, to keep blood pressure below 140/90 mmHg. The standard group received medication only if a participant developed more severe hypertension, or a blood pressure greater than 160/105 mmHg. Participants were evaluated in routine clinic visits through six weeks after delivery.

There was an almost 20 percent decrease in pregnancy complications for women treated with medication compared to the standard group. Complications included severe preeclampsia and preterm births before 35 weeks’ gestation.

Preeclampsia, a pregnancy complication that occurs after 20 weeks’ gestation, affects 2 to 8 percent of pregnancies in the United States but affects more than 30 percent of pregnant women with chronic hypertension. Women with preeclampsia experience hypertension and sometimes signs of damage to other organ systems, such as the brain, liver and kidneys. In the active group, severe preeclampsia was reduced from 29 to 23 percent.

Preterm births before 35 weeks’ gestation were also significantly reduced in the active group, from more than 16 to 12 percent. Babies born before 35 weeks have an increased chance for short-term morbidities, long-term health complications, and intellectual and developmental disabilities.

Additionally, the active group saw reductions in frequency of severe maternal hypertension, any preeclampsia with or without severe features, and any preterm birth before 37 weeks. There was slight or no difference in maternal cardiovascular complications and neonatal complications between the two study groups. Importantly, newborn size was also not affected by treatment.

The original version of this news release was issued by UAB.

NIH adds to CHAP funding

The National Institutes of Health awarded additional funding to the CHAP consortium in September 2021 to follow mothers enrolled in the program until five to 10 years after their completion of the trial to examine the long-term trajectory of hypertension and cardiovascular outcomes. Additional funding to study preeclampsia epigenetics using samples from the CHAP trial was also awarded in February 2022. These studies, including a potential study of childhood outcomes, will provide a more comprehensive view of the effects of treatment of chronic hypertension with medication during pregnancy.

The CHAP consortium included more than 60 clinical sites across the United States. Columbia University, University of North Carolina-Chapel Hill, University of Pennsylvania, University of Texas at Houston, Duke University, Stanford University, WakeMed Hospital, University of California-San Francisco, St. Luke’s University Health Network, Baylor College of Medicine and Texas Children’s Hospital, University of Oklahoma, MetroHealth System, Indiana University, Drexel University, University of Utah, University of Texas Southwestern, Intermountain Healthcare, Ochsner Baptist Medical Center, Christiana Care Health Services, University of Texas Medical Branch, UnityPoint Health – Meriter Hospital, Marshfield Clinic, St. Peters University Hospital, Washington University, University of Mississippi Medical Center-Jackson, UPMC Magee-Womens Hospital, University of Pittsburgh and NewYork-Presbyterian were among the partners with UAB in the project.