High blood pressure in pregnancy may be rising—especially among Millennial and Gen Z moms

That’s the result of a study in JAMA Network Open. It found that hypertensive disorders doubled among women who had a child between 2015 and 2019 if they were born between 1996 and 2004 compared to women born between 1951 and 1959 who gave birth between 1995 and 1999. It’s now estimated that 8% of pregnant individuals will have high BP in their pregnancies.

“We were surprised that, despite advances in medical technology, Millennials and Gen Zers are two times as likely to develop high blood pressure during their first pregnancy than were Baby Boomers even after accounting for their age during pregnancy,” Natalie A. Cameron, MD, an instructor at Northwestern Medicine and one of the researchers, tells Motherly. 

Crunching the numbers

The study looked at nearly 4 million women with a first pregnancy who gave birth between 1995 and 2019. Of the participants, 57.8% were non-Hispanic white, 20.2% were Hispanic, 13.9% were non-Hispanic Black, 6.5% were non-Hispanic Asian or Pacific Islander, and 0.8% were non-Hispanic American Indian or Alaska Native. 

Women who delivered between 2015 and 2019 had a 59% greater risk of having a hypertensive disorder during pregnancy. There was a 161% greater risk in first-time mothers born between 1996 and 2004. Most of the women from each delivery period received prenatal care during their first trimester.

Related: 7 ways to lower blood pressure during pregnancy

Even though Dr. Cameron’s team noted differences in hypertension during pregnancy among racial and ethnic groups, “these differences do not reflect biological or genetic causes,” she notes. 

“Rather, these differences reflect neighborhood, economic and health-systems level factors that shape access to care and health during pregnancy,” she adds.

Taking care of your blood pressure in pregnancy

Dr. Cameron says that preventing high blood pressure in pregnancy starts by optimizing heart health before pregnancy. (You can always take steps to do it during pregnancy, though.)

“This means eating a healthy diet that is low in salt, staying active and striving to maintain a normal body weight,” she says.

Related: 15 fertility superfoods to add to your get-pregnant meal plan

See your doctor before pregnancy to screen for and control high blood pressure. Once pregnant, talk to your doctor about risk factors for high blood pressure, such as clinical obesity or diabetes. You should see if taking a low-dose aspirin could help prevent preeclampsia, Dr. Cameron says.

Medications can control blood pressure, though there are still investigations ongoing to see which drugs are best to prevent and treat high BP during pregnancy (and in the weeks after pregnancy), Dr. Cameron adds.

Why poor heart health is on the rise

What’s causing the increase in BP problems? Dr. Cameron says that even though we may be better at detecting high BP during pregnancy, she thinks poor heart health prior to pregnancy has a role. 

“Rising obesity rates, as well as higher consumption of processed foods and more time spent sitting are likely culprits,” she adds.

That’s why researchers need to examine those risk factors with more research. 

Related: Pressured to lose weight before fertility treatments? One study shows it’s not necessary

Michael Miller, MD, a cardiologist and chief of medicine at the Corporal Michael J. Crescenz VA Medical Center in Philadelphia, tells Motherly that because this is an observational study, it’s limited in directly identifying causes. 

“Nevertheless, the results are worrisome and add to the growing concern of elevation in risk factors that are not well controlled,” Miller notes. 

Specifically, the primary risk factor for high blood pressure and preeclampsia is increasing maternal age (as was the case in the study). But obesity, smoking, diabetes, and pre-existing hypertension were not measured, Dr. Miller says. 

Related: It’s science: Your blood pressure *before* you get pregnant could determine your baby’s sex

The prevalence of all these risk factors (except smoking) has increased in this age group, he says.

“The major flaw of this study was not having these data to assess,” Dr. Miller adds.

Here’s another fun fact: If women earlier on didn’t report their high BP, that could impact how the data was interpreted, adds Yvette LaCoursiere, MD, an OB/GYN at UC San Diego Health, who was not affiliated with the research.

But the study wasn’t out to explain the causes of the hypertension trend–instead, it merely uncovered it, Dr. LaCoursiere adds.

“This study should not be interpreted to simply say that there is an intrinsic increase in hypertension in pregnancy,” she explains. Instead, there are likely “modifiable cardiovascular risk factors that are contributing to the finding of increasing hypertension in pregnancy.”

Cardiovascular health is important but often overlooked

Another recent study in “Circulation” stressed the importance of cardiovascular health before, during, and after pregnancy. (Cameron led that one, too.) Because pregnancy can tax the heart and circulatory system, it’s important to take preventive measures where you can.

Researchers say “optimal” pre-pregnancy heart health went down more than 3% between 2016 and 2019. They said weight, diabetes status and hypertension are big players in terms of what’s causing poor heart health.

More than half of women between 20 and 44 who had a baby in America during 2019 had at least one cardiovascular risk factor before conceiving, the study in Circulation notes.

Sources

Cameron NA, Petito LC, Shah NS, et al. Association of Birth Year of Pregnant Individuals With Trends in Hypertensive Disorders of Pregnancy in the United States, 1995-2019. JAMA Netw Open. 2022;5(8):e2228093. 

Cameron NA, Freaney PM, Wang MC, Perak AM, Dolan BM, O’Brien MJ, Tandon SD, Davis MM, Grobman WA, Allen NB, Greenland P. Geographic Differences in Prepregnancy Cardiometabolic Health in the United States, 2016 Through 2019. Circulation. 2022 Feb 15;145(7):549-51.