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New research shows that 1 in 10 pregnant people may develop hypertension within a year of childbirth despite no prior history of high blood pressure. Igor Alecsander/Getty Images
  • New research shows that 1 in 10 pregnant people may develop hypertension within a year of giving birth, even with no prior history of high blood pressure.
  • The highest risk was associated with people over 35, current or former smokers, or people who delivered their babies by c-section.
  • Black people faced an even higher risk of developing hypertension after childbirth when all three risk factors were present.
  • All pregnant people, especially those over 35, should work with their doctors to manage their blood pressure levels throughout their pregnancy and during the postpartum period.

Pregnancy and childbirth may raise the risk of hypertension — even in people with no prior history of high blood pressure before or during pregnancy.

A new study led by a researcher at Boston University School of Public Health (BUSPH) found that roughly 1 in 10 people developed first-time hypertension within a year following childbirth.

In more than 20% of these cases, the subjects developed hypertension more than 6 weeks following delivery.

“The study findings have implications for postpartum care, particularly among patients without a history of hypertension,” Samantha Parker, PhD, lead author of the study and an assistant professor of epidemiology at BUSPH, said in a press release.

“We were surprised at the number of cases captured more than 6 weeks after delivery, a period that falls well outside of routine postpartum follow-up.”

The research was recently published in Hypertension, a journal of the American Heart Association (AHA).

To conduct the new study, Parker and her co-authors reviewed the medical records of 3,925 pregnant people who’d given birth at Boston Medical Center between 2016 and 2018.

They excluded pregnant people who had a prior history of chronic hypertension, as well as those who had developed preeclampsia during pregnancy. Preeclampsia is a hypertensive disorder that causes high blood pressure and other potential complications in pregnancy.

When the researchers analyzed subjects’ blood pressure measurements from before they gave birth to a year following delivery, they found that 1 in 10 developed first-time postpartum hypertension within a year following childbirth.

Subjects were more likely to develop postpartum hypertension if they were older than 35 years, were current or former smokers, or delivered their baby by cesarean section (C-section).

Among those with all three risk factors present, 29% developed new postpartum hypertension. That risk increased to 36% among non-Hispanic Black pregnant people.

Other risk factors for postpartum hypertension included type 2 diabetes (T2D), a body mass index (BMI) score of 40 or more, and a history of illicit drug use.

The findings are consistent with past research that has shown that Black people have an increased risk of postpartum hypertension and other complications of pregnancy and childbirth.

These inequities may be due, in part, to the health effects of structural racism and discrimination.

“Understanding this relationship between pregnancy and hypertension is particularly important in addressing inequities in maternal cardiovascular disease and death for People of Color,” Parker said.

More research is necessary to identify, understand, and learn how to best manage the risk factors for postpartum hypertension.

Older age, high BMI, T2D, and a history of smoking or substance use are all known risk factors for hypertension in general.

The authors of the new study didn’t have the data needed to evaluate other traditional risk factors for hypertension, such as diet, physical activity level, or cholesterol levels.

As for c-sections, Parker told Healthline that people who deliver by this method may be more likely to get a diagnosis of postpartum hypertension because they tend to have more follow-up visits than those who deliver vaginally.

In other words, postpartum care for c-sections may provide more opportunities to diagnose hypertension. It’s also possible that c-sections or related treatments may raise the risk of hypertension.

“Some medications used to treat pain, such as NSAIDs, have been shown to increase blood pressure, and these medications are more commonly used by patients with c-sections,” Parker said.

Postpartum hypertension may raise a person’s risk of stroke, cardiovascular disease (CVD), and chronic kidney disease later in life, which is why it’s important to diagnose and manage it early.

“Childbirth in itself is a great opportunity to improve management of cardiovascular risk, as it provides women who are otherwise generally considered ‘young and healthy’ with encounters with a healthcare provider that may have otherwise not occurred for a while,” Dr. Eran Bornstein, the vice chair of obstetrics and gynecology at Lenox Hill Hospital in New York, told Healthline.

“If appropriately screened for their cardiovascular risk including hypertension during pregnancy, delivery, or postpartum, such women may be referred to a cardiologist for assessment, surveillance, and management of their cardiovascular health issues, as well as maintain ongoing care after delivery,” he added.

But current standards of postpartum care may limit opportunities for healthcare professionals to diagnose and treat postpartum hypertension that develops after childbirth.

That’s because standard postpartum care includes only one clinic visit within 4 to 6 weeks following delivery. As a result, postpartum hypertension that develops more than 6 weeks following childbirth may go undiagnosed.

Moreover, not all people who give birth receive standard postpartum care.

“In the [United States), because we have no [federally] mandated maternity leave, the majority of women do not even make their postpartum 6-week follow-up visit,” Dr. Martha Gulati, a cardiologist at Cedars-Sinai Heart Institute in Los Angeles, CA, who specializes in women’s heart disease prevention, told Healthline.

“We need women to get their postpartum visits — and we also need policies in place to ensure women have care beyond 6 weeks postpartum. Additionally, until we have mandated federal maternity leave for women, the most vulnerable women are at the greatest risk of not being diagnosed or treated for something that is very treatable,” Gulati noted.

To help manage the cardiovascular risks of pregnancy and childbirth, Bornstein encouraged people who are pregnant or planning to get pregnant to speak with their obstetricians about their personal and family medical history.

If the person already has hypertension or they’re at high risk of developing hypertension or other cardiovascular complications during or after pregnancy, their obstetrician may refer them to a maternal-fetal medicine specialist, and in some cases, a cardiologist or blood pressure specialist.

“Prior to pregnancy, this team will focus on comprehensive assessment of the severity of the condition, make sure that planned pregnancy is safe, and optimize the health conditions in order to reduce potential pregnancy complications,” Bornstein said.

“During pregnancy, this team will focus on [the] management of the underlying issues — control of blood pressure, for example, [or] diabetes control.”

The pregnant person’s healthcare team will also monitor them and the fetus for potential complications.

Depending on the pregnant person’s risk factors, their healthcare professional may prescribe low-dose aspirin to lower the risk of preeclampsia during pregnancy or manage the cardiovascular risks following preeclampsia.

“Following delivery, assuring ongoing surveillance with the appropriate health care provider and self-monitoring of blood pressure [is] key,” Bornstein said.

New research shows that as many as 1 in 10 people may develop hypertension following childbirth, even with no prior history of high blood pressure.

Certain health conditions such as obesity, type 2 diabetes, and a history of drug use may increase a pregnant person’s risk for developing hypertension.

Pregnant people over 35 with a history of smoking or who delivered via c-section face a higher risk. When these three risk factors were present, the association is highest among Black people. This discrepancy may also be attributed to systemic issues like racial discrimination and barriers to healthcare.

To prevent hypertension following childbirth, pregnant people should work with their doctors to control their blood pressure levels throughout their pregnancy and during the first year postpartum.