Pregnancy is a time of excitement, hope, and anxiety. However, it can also be a particularly scary journey for moms-to-be who have elevated blood pressure, or prehypertension — a condition in which blood pressure numbers are higher than normal but not high enough to be considered full-on hypertension. As it turns out, pregnant women with prehypertension have increased cardiovascular risk and are more likely to develop metabolic syndrome after giving birth, according to new research published in Hypertension.

Hypertension, also known as high blood pressure, is often referred to as “the silent killer” because it typically comes without signs or symptoms. Yet, it is one of the leading causes of premature death worldwide. Unfortunately, nearly 1 of 3 American adults experience persistent blood pressure elevations in the upper ranges of normal, and therefore risk developing the condition.

Current blood pressure guidelines do not distinguish between pregnant women and the general population, so hypertension is defined as having blood pressure that is 140/90 mm/Hg or above — the top number being systolic blood pressure and the bottom being diastolic. People with a systolic blood pressure (pressure in the arteries when the heart beats) of 120 to 139 mm/Hg and a diastolic pressure (pressure between heart beats, when the heart rests) of 80 to 89 mm/Hg are diagnosed with prehypertension. For reference, normal blood pressure should be less than 120/80 mm/Hg for adults aged 20 and older, Medical Daily previously reported.

Researchers found that prehypertensive pregnant women are 6.5 times more likely than those with normal blood pressure to develop metabolic syndrome — a group of conditions, such as high blood pressure, high blood sugar, and abnormal cholesterol levels, which increase risk of heart disease, stroke, and diabetes after giving birth.

"Our findings underscore an important issue that has been long ignored in clinical practice — the fact that criteria for hypertension in pregnancy are derived from the general population," lead investigator Dr. Jian-Min Niu said in a statement."We anticipate that if reaffirmed in further research, our study could spark a change in what we currently deem healthy blood pressure in pregnant women."

For the study, Niu and her colleagues looked at data collected from 507 Chinese women with uncomplicated pregnancies, no history of hypertension ,and normal blood sugar and cholesterol. The women underwent seven or more blood pressure measurements during their pregnancies, along with other tests typically used to monitor pregnancy, including weight measurements and fetal ultrasounds. They continued taking tests once every few months for a year-and-a-half after giving birth.

The study participants were grouped into three categories based on their blood pressure levels: those whose blood pressure remained on the lower end of normal throughout pregnancy (34 percent), those whose blood pressure hovered around midpoint-normal (52 percent), and those whose readings trended in the higher end of normal or prehypertensive (13 percent). In the statement, researchers said that a series of measurements during a woman’s lifetime did not predict risk of metabolic syndrome, but that patterns of repeated elevations over the course of a pregnancy did.

"Blood pressure measurements are already done as a matter of routine and cost-effective checkups during pregnancy, so our findings underscore this tool's potential to gauge a woman's post-partum cardiovascular risk," Niu said. "Early identification of metabolic risk factors and implementation of lifestyle modifications may help delay the onset of cardiovascular disease that would present itself 20 to 30 years after delivery."

In other words, pregnancy can be seen as a cardiovascular stress test for women in the sense that it can “reveal underlying disturbances in blood pressure regulation, glucose, and cholesterol metabolism,” researchers wrote in a news release. If these three areas are plagued by abnormalities, then they are likely to have disrupted cardiovascular functions, which can eventually lead to cardiovascular disease.

Prehypertension doesn’t only put the mother at risk. Past research has found that pregnant women who experience higher blood pressure than normal or persistent blood pressure elevations in the upper ranges are more likely to give birth to an underweight or stillborn baby.

Source: Niu J, Li y, Lei Q, et al. Prehypertension During Normotensive Pregnancy and Postpartum Clustering of Cardiometabolic Risk Factors: A Prospective Study. Hypertension. 2016.