The prevalence of chronic hypertension in pregnancy in the United States doubled from 2007-2021, but only about 60% of those with the potentially life-threatening condition were treated with antihypertensive medications, according to a National Institutes of Health (NIH)-supported study of nearly 2 million pregnancies. The study, which was funded by NIH's National Heart, Lung, and Blood Institute (NHLBI), did not explore the reasons for the increase, but rising maternal age, growing obesity rates, and other factors likely played a role, according to researchers. The findings were published today in the journal Hypertension.
"These findings are deeply concerning because of the high rate of U.S. maternal mortality, which is linked to chronic hypertension in pregnancy," said study lead Stephanie Leonard, Ph.D., an epidemiologist at Stanford University School of Medicine in California. "Despite the availability of safe and effective treatments for chronic hypertension, the study speaks to an urgent need for improvement in care for this serious condition."
Chronic hypertension in pregnancy is defined as having persistent high blood pressure - 140/90 millimeters of mercury (mm Hg) or higher - before pregnancy or within 20 weeks of gestation. The condition can cause organ damage in the expectant mother and increase the risk of preterm birth or a low birthweight baby. It can be fatal if undetected and untreated.
The study has particular relevance for Black, American Indian, and Alaska Native people, who experience the nation's highest rates of poor maternal health outcomes and pregnancy-related deaths.
"We need to better understand gaps in treatment for chronic hypertension, especially in these high-risk groups," said Candice A. Price, Ph.D., a program director at NHLBI, who specializes in women's health research. "If we're not detecting and treating chronic hypertension early, that's a missed opportunity for protecting heart health during and after pregnancy."
For the study, researchers used a large database of U.S. commercial insurance claims from 2007-2021 to analyze the prevalence of chronic hypertension among 1.9 million pregnant people ages 12-55 years old, as well as the use of oral antihypertensive medication during this time.
The researchers found the percentage of those pregnant who had chronic hypertension more than doubled - from 1.8% in 2008 to 3.7% in 2021. They also found that among those with chronic hypertension, the percentage who used antihypertensive medication remained steady during the study period - rising from 58% to only 60%.
While the reason for the sharp increase in chronic hypertension in pregnancy was not the focus of this study, Leonard noted that the rise was consistent with hypertension trends observed during various periods before the current study, as well as trends in the general U.S. adult population.
A prior analysis of national data from 1970 to 2010, for example, suggested that the increasing trend in chronic hypertension in pregnancy was attributable in part to women having babies at an older age. In the current study, women with chronic hypertension tended to be older than those without the condition, the researchers confirmed.
Rising rates of obesity could also contribute to the increase, as could other factors, such as increased vigilance in diagnosing chronic hypertension and better medical record-keeping of its incidence.
Leonard and colleagues analyzed the potential impact of the updated hypertension guidelines of the American College of Cardiology and American Heart Association in 2017, which lowered the threshold for diagnosing hypertension for all adults. However, they found no association, at least for now.
Blood pressure criteria changed from 140-159/90-109 mm Hg to 130-139/80-89 mm Hg for diagnosis of stage 1, and from greater than or equal to 160/110 mm Hg to greater than or equal to 140/90 mm Hg for stage 2, which carries the greatest risk to health. Leonard said it is possible that the impact from the guidelines could show up in analyses of the years after the 2008-2021 period she and her team studied.
To manage hypertension during pregnancy, experts recommend that women check their blood pressure at home and keep it under control, visit with a doctor often, and take antihypertensive medications as prescribed.
This study was supported by grants K01HL171699 and R01HL139844 from NHLBI and award UL1TR003142 from the NIH's National Center for Advancing Translational Science Clinical and Translational Science.
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