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Treating high blood pressure during pregnancy is safe and may be helpful at lower thresholds than previously thought, a new scientific report says.

"For decades, the benefits of blood pressure treatment for pregnant women were unclear," Dr. Vesna D. Garovic said in a news release. She led a committee of experts that reviewed and analyzed existing research. "And there were concerns about fetal well-being from exposure to antihypertensive medications."

But the report, published Wednesday as a from the ·¬ÇÑÊÓƵ in its journal Hypertension, said treatment may reduce a woman's risk for severe high blood pressure without endangering her child.

High blood pressure, or hypertension, during pregnancy is a major cause of complications and death for mothers and their babies, and it increases women's short- and long-term risks for cardiovascular disease. It also increases the risk for preterm delivery and low birthweight.

Among high-income countries, the U.S. has one of the highest maternal mortality rates for high blood pressure-related problems. Cardiovascular disease, including stroke and heart failure, now accounts for up to half of all maternal deaths in the U.S., where pregnancy-related stroke hospitalizations increased more than 60% from 1994 to 2011.

In the U.S., high blood pressure during pregnancy disproportionately affects women who are Black, American Indian or Alaska Native.

"Given the rising number of cases of hypertension during pregnancy, together with hypertension-related complications, the problem has become a public health crisis, particularly among women from racially and ethnically diverse backgrounds," said Garovic, a professor of medicine at Mayo Clinic in Rochester, Minnesota.

A scientific statement is an expert analysis of current research and may inform future clinical practice guidelines. This one was written by experts in obstetrics and gynecology, maternal-fetal medicine, cardiology, nephrology, hypertension and internal medicine.

Hypertension during pregnancy is the . Severe cases are associated with increased risks of heart-related complications for mothers both immediately after delivery and for years later.

Because of concerns about how medications may affect the fetus, treatment guidelines vary.

Since 2017, the AHA and the American College of Cardiology have defined high blood pressure in the general population as a systolic (top) reading of at least 130 mmHg or a diastolic (bottom) reading of at least 80 mmHg.

Most guidelines worldwide define high blood pressure during pregnancy as a reading of 140/90. In the U.S., the American College of Obstetricians and Gynecologists recommends starting treatment at 160/110. Other guidelines recommend starting treatment at 140/90.

The statement said the latest research indicates use of blood pressure-lowering medicine during pregnancy does not appear to harm fetal development. And preventing high blood pressure during pregnancy supports maternal health both during and after pregnancy. Women who have hypertension during pregnancy are more likely to develop sustained high blood pressure after pregnancy at a higher rate compared to those whose blood pressure was normal during pregnancy.

"Future clinical trials are needed to address questions about when to begin treatment for high blood pressure during pregnancy," Garovic said. But, she said, it was "reassuring" that the statement's comprehensive review of research showed "emerging evidence that treating high blood pressure during pregnancy is safe and effective and may be beneficial at lower thresholds than previously thought."

Reducing severe high blood pressure may be particularly important in communities that lack resources and expertise to respond to hypertension emergencies, the statement said.

It also reinforces recent research that suggests lifestyle changes before and during pregnancy can improve maternal and fetal outcomes. For example, dietary changes before and during pregnancy can limit weight gain and improve pregnancy outcomes. And exercise during pregnancy may reduce the risk of gestational hypertension by about 30% and of preeclampsia by about 40%.

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