Treating high blood pressure during pregnancy is safe for the baby, study finds

Treating high blood pressure in pregnant women reduced their risk of developing severe preeclampsia and helped prevent some premature births, the study found. Photo courtesy of Max Pixel

When women start a pregnancy with mild high blood pressure, treating the condition can reduce the risk of health threats to them and their babies, according to a new clinical trial.

Experts said the findings could change the way many women manage their blood pressure during pregnancy.

Until now, the value of treating pregnant women for milder chronic hypertension was unclear. And it was feared that it could reduce blood flow to the fetus, which could harm growth.

In the findings of the new trial, published recently in the New England Journal of Medicine, those fears did not come true. Instead, treating the women reduced their risk of developing severe preeclampsia – a dangerous complication of pregnancy – and helped prevent some premature births.

Dr Kjersti Aagaard, one of the trial’s researchers, said the results should change practice.

“This is one of those rare essays where you say, ‘Yes, I’m going to do something different tomorrow than I do today,'” said Aagaard, professor of obstetrics and gynecology. at Baylor College of Medicine in Houston. .

These are women who become pregnant with chronic high blood pressure, which differs from the form that occurs in some women during pregnancy.

When people who are not pregnant have high blood pressure, drug treatment is the norm. But treatment during pregnancy has been more controversial.

Experts agreed that treatment is necessary when a pregnant woman’s chronic high blood pressure is severe – about 160/110 mm Hg or higher. But there were no clear guidelines on how to handle the gentler elevations.

The bottom line is that treatment is “everywhere,” said Dr. Michael Greene, professor emeritus of obstetrics and gynecology at Massachusetts General Hospital/Harvard Medical School.

In some cases, a woman and her doctor may decide to treat the condition. But often, treatment is withheld unless a woman’s blood pressure numbers reach the severe range. Sometimes, Greene added, a woman who was already taking blood pressure medication before pregnancy will be taken off it.

Greene, who co-wrote an editorial published with the study, noted that one trial’s results may not convince everyone.

“But as a provider, I say, yes, this should change the way pregnant women are treated for chronic hypertension,” he said.

The trial involved more than 2,400 pregnant women at medical centers across the United States. All had milder chronic hypertension. Half were randomly assigned to “stricter” management, which involved the use of drugs to bring their numbers below 140/90 mm Hg. The other half were only started on medications if her blood pressure was 160/105 mm Hg or higher.

Tighter control, according to the trial, reduces a woman’s risk of developing severe preeclampsia, a condition characterized by high blood pressure and signs of dysfunction of vital organs like the kidneys and liver. When preeclampsia is severe, doctors may need to induce labor or perform a caesarean section to deliver the baby sooner.

In the trial, 23% of women with tighter blood pressure control developed preeclampsia with “serious features”, compared with 29% of women in the comparison group.

Similarly, the likelihood of needing a “medically indicated” delivery before the 35th week of pregnancy was reduced – to 12% in women with tighter blood pressure control, compared to almost 17% in the group. of comparison.

These are important differences for women, babies and public health, said Dr Emre Seli, scientific director of the non-profit organization March of Dimes.

“The United States has a high preterm birth rate, around 10 percent,” Seli said. “It’s not a rare occurrence.”

He also noted that the trial included many women of color, who are disproportionately affected by these pregnancy complications. About 48% of the participants were black and 20% were Hispanic.

Seli said the results underscore the importance of entering pregnancy in good cardiovascular health – which ideally includes not smoking, regular moderate exercise, being at a healthy weight and having a healthy blood pressure.

While medication is needed, Greene noted, some high blood pressure medications are contraindicated in pregnancy, including ACE inhibitors. He said women with high blood pressure who are considering pregnancy should speak to their doctor to ensure they are taking appropriate blood pressure medication.

As for pregnant women wondering if their blood pressure is optimally controlled, Aagaard said: “Talk to your doctor. Ask them about this trial and if they’ve ever had a chance to read it.”

The research was funded by the US National Institutes of Health.

More information

The March of Dimes has more on managing high blood pressure during pregnancy.

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