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Kaiser Permanente study evaluates joint impacts of chronic hypertension and hypertensive disorders developing during pregnancy on severe maternal adverse outcomes

Patients with chronic hypertension had lower rates of life-threatening outcomes comparable to no hypertensive disorders of pregnancy when they avoided preeclampsia

The risk of serious adverse outcomes of pregnancy for women with chronic hypertension who did not develop preeclampsia was nearly the same as the risk for women without chronic hypertension or hypertensive disorders developing during pregnancy, a new Kaiser Permanente study shows.

The research, published in JAMA Network Open, also found that the risk of experiencing a life-threatening complication at delivery was almost 2 times higher for those who developed gestational hypertension, and 5 times higher for both women with and without chronic hypertension who developed preeclampsia.

Erica Gunderson, PhD, MPH

“Previous studies have not been able to differentiate the impacts of various combinations of pre-existing hypertension and developing hypertensive conditions during pregnancy on the risk of severe maternal morbidity,” said lead author Erica P. Gunderson, PhD, MPH, a senior research scientist at the Kaiser Permanente Northern California Division of Research and a professor at the Kaiser Permanente School of Medicine. “This study uniquely evaluated risk levels in patients without pre-existing conditions in order to isolate the effects attributed to pregnancy in relation to severe maternal morbidity outcomes, which include these disorders.”

The retrospective study included 249,892 pregnant patients who did not have chronic hypertension and 13,626 pregnant patients with chronic hypertension. None of the patients with chronic hypertension also had a diagnosis of heart, kidney, or liver disease. All the patients gave birth between 2009 and 2019.

The study showed that the relative risk of developing a severe adverse outcome of pregnancy — these include kidney failure, heart failure, heart attack, stroke and eclampsia (seizures) — was about 5 times higher for pregnant patients with or without chronic hypertension who went on to develop preeclampsia than it was for patients who had pre-existing hypertension and no pregnancy-related high blood pressure problems.

“This study focused on women with chronic hypertension who did not have pre-existing diseases and found that those who did not develop preeclampsia had a much lower risk of adverse events — and that this risk was nearly the same as what we saw in women without chronic hypertension or hypertensive disorders of pregnancy,” said Gunderson. “The importance of preventing hypertensive disorders of pregnancy, especially among women with chronic hypertension, is paramount to reduction of serious adverse health outcomes related to pregnancy.”

An unhealthy combination

High blood pressure and pregnancy are a potentially unhealthy combination for both mothers and their babies. In maternity care, patients who have high blood pressure before becoming pregnant or develop it early in pregnancy are classified as having chronic hypertension. These patients make up about 5% to 8% of all pregnancies.

James M. Roberts, MD

“Our study underscores the need for physicians to understand the unique risks of hypertensive women who do not have evidence of heart, kidney, or liver disease,” said senior author James M. Roberts, MD, a professor of obstetrics, gynecology, and reproductive science at the University of Pittsburgh. “This is likely the most common form of hypertension in women of reproductive age, and for these women a focus on preventing preeclampsia with aspirin and behavioral modifications is critical.”

Pregnant individuals without chronic hypertension are at risk of developing high blood pressure after 20 weeks of pregnancy, a condition called gestational hypertension. Preeclampsia is a related but separate condition that also can start after 20 weeks of pregnancy that may develop in women with or without chronic hypertension. It is marked by high blood pressure, high levels of protein in the urine (a sign of kidney damage), or damage to the liver, lungs, heart, or eyes. It can also cause a stroke or other brain injuries.

 

The importance of preventing hypertensive disorders of pregnancy, especially among women with chronic hypertension, is paramount to reduction of serious adverse health outcomes related to pregnancy.  — Erica Gunderson, PhD, MPH

 

The researchers found that 4.7% of the patients who did not have chronic hypertension developed preeclampsia during pregnancy compared to 31.5% of the patients with chronic hypertension.

“To prevent severe maternal adverse outcomes, identifying and treating hypertension before pregnancy, and interventions during early pregnancy are crucial,” said Gunderson. “Preeclampsia prevention in patients with or without chronic hypertension is key to reduction in maternal morbidity and mortality. Almost one in three pregnant individuals with chronic hypertension will develop preeclampsia during their pregnancy with serious consequences.”

Homing in on risk

The study ascertained risk of severe maternal morbidity at delivery hospitalization among joint subgroups of no chronic hypertension and chronic hypertension with or without developing hypertensive disorders of pregnancy. The patients were classified into 5 subgroups: 1) patients with chronic hypertension who developed preeclampsia; 2) patients with chronic hypertension who did not develop preeclampsia; 3) patients who did not have chronic hypertension and developed preeclampsia; 4) patients who developed high blood pressure during pregnancy (gestational hypertension); and 5) patients who did not have chronic hypertension and did not develop preeclampsia or gestational hypertension (lowest risk group).

Mara Greenberg, MD

The study found 934 life-threatening pregnancy-related cases per 10,000 births in the patients with no chronic hypertension who developed preeclampsia and 878 cases per 10,000 births in those with chronic hypertension who developed preeclampsia. In contrast, 195 severe pregnancy-related complications per 10,000 births were seen in patients with chronic hypertension who did not develop preeclampsia; 312 per 10,000 were seen in patients who developed gestational hypertension; and 165 per 10,000 births were seen in patients who did not have chronic hypertension and who did not develop preeclampsia or gestational hypertension.

Treatment for gestational hypertension or preeclampsia includes lifestyle interventions, such as diet and physical activity, monitoring of the pregnant patient and baby, medications to lower blood pressure, medications to treat any other symptoms that develop, and, potentially, delivering the baby early.

“This study identifies more clearly than ever before that development of preeclampsia is really a sentinel event we must learn how to prevent,” said co-author Mara Greenberg, MD, a maternal-fetal medicine specialist with The Permanente Medical Group who directs the Regional Perinatal Service Center. “It’s also important that our current efforts to understand how to prevent underlying hypertension and prevent preeclampsia among all pregnant patients be undertaken with an equity focus. We know that exposure to racism that impacts communities of color results in a disproportionate burden of both underlying hypertension and preeclampsia.”

The study was funded by the National Heart, Lung and Blood Institute

Co-authors include Baiyang Sun, PhD, Stacey E. Alexeeff, PhD, Janet Alexander, MPH, and Mai N. Nguyen-Huynh, MD, of the Division of Research; Michael Najem, MD, of the Kaiser Permanente Bernard J. Tyson School of Medicine; Mara Greenberg, MD, of The Permanente Medical Group; and James M. Roberts, MD, University of Pittsburgh.

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About the Kaiser Permanente Division of Research

The Kaiser Permanente Division of Research conducts, publishes and disseminates epidemiologic and health services research to improve the health and medical care of Kaiser Permanente members and society at large. It seeks to understand the determinants of illness and well-being, and to improve the quality and cost-effectiveness of health care. Currently, DOR’s 600-plus staff is working on more than 450 epidemiological and health services research projects. For more information, visit divisionofresearch.kaiserpermanente.org or follow us @KPDOR.

 

 

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