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A recent study published in the New England Journal of Medicine – and co-authored by a faculty member in the Indiana University School of Medicine Department of Obstetrics and Gynecology – found that treating mild chronic hypertension during pregnancy can benefit both the parent and the child.

Study: Treating preexisting high blood pressure in pregnancy improves maternal and fetal outcomes

A recent study published in the New England Journal of Medicine – and co-authored by a faculty member in the Indiana University School of Medicine Department of Obstetrics and Gynecology – found that treating mild chronic hypertension during pregnancy can benefit both the parent and the child.

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; but treating non-severe or mild forms of chronic hypertension during pregnancy has led to a divide in medical recommendations for decades.

The new study provides evidence that treating mild chronic hypertension with medications is safe. The findings provide for the first time comprehensive, evidence-based data for treating non-severe forms of chronic hypertension during pregnancy, according to a news release.

The results are from the Chronic Hypertension and Pregnancy (CHAP) trial consortium of more than 60 clinical sites across the United States that was led by the University of Alabama at Birmingham. Indiana University is among the collaborators. David Haas, MD, MS, the Robert A. Munsick Professor of Obstetrics and Gynecology, led the IU site for the study.

“We are very excited to have been a part of this important study that will impact clinical care and improve outcomes for so many pregnant patients and their babies,” Haas said. “We are also excited that we are going to continue to follow these families to look at long-term health impacts as well.”

The trial evaluated the effects of prescribing blood pressure medication to pregnant patients 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. The new data will likely prompt clinicians to reevaluate recommendations and practice guidelines and start treating more cases of chronic hypertension in pregnant patients.

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 launched 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.

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. It is characterized by 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.

Read the full news release here

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IU School of Medicine

With more than 60 academic departments and specialty divisions across nine campuses and strong clinical partnerships with Indiana’s most advanced hospitals and physician networks, Indiana University School of Medicine is continuously advancing its mission to prepare healers and transform health in Indiana and throughout the world.

The views expressed in this content represent the perspective and opinions of the author and may or may not represent the position of Indiana University School of Medicine.