New Definitions of Hypertension Reveal New Preeclampsia Risks

Jennie Smith

June 19, 2020

Using the new clinical definitions of hypertension, pregnant women with even modest elevations in blood pressure (BP) are at increased risk for preeclampsia, according to results from a large retrospective cohort study.


In a 2017 guideline, the American College of Cardiology and American Heart Association changed clinical definitions of hypertension in adults. People previously deemed to have prehypertension were classed as having elevated blood pressure (systolic BP 120-129 mm Hg and diastolic BP >80 mm Hg) or stage 1 hypertension (systolic 130-139 mm Hg or diastolic 80-89 mm Hg).

And while hypertension as earlier defined (at or above systolic 140 mm Hg or at or above diastolic 90 mm Hg; now called stage 2 hypertension) has been long associated with adverse maternal and fetal effects, it was unclear whether lesser elevations in blood pressure also are linked to the same.

For their research published in Obstetrics & Gynecology, Elizabeth F. Sutton, PhD, of the University of Pittsburgh and colleagues looked at records from 18,162 women who had given birth to a single baby and had two or more prenatal appointments before week 20 of pregnancy. The women in the study were seen at the same institution over a 3-year period ending in 2018. Three-quarters of the cohort had normal blood pressure, while 14% had elevated blood pressure and 5% had stage 1 hypertension before 20 weeks. Another 6% of the cohort had stage 2 hypertension.

The authors found preeclampsia risk increased with increasing blood pressure elevation. Among women with normal blood pressure before 20 weeks' gestation, 5% had preeclampsia, while 7% of those with elevated blood pressure did, as did with 12% of women with stage 1 hypertension and 30% of women with stage 2 hypertension. The increase in risk of preeclampsia was because of preterm preeclampsia in the women with elevated blood pressure. Both term and preterm preeclampsia were factors in women with stage 1 and stage 2 hypertension, but preterm preeclampsia was associated with a higher risk. Although black race was associated with a higher risk of preeclampsia, the pattern of increasing risk with higher blood pressure category was similar in both black and white women.

Researchers also looked at gestational diabetes, severe maternal morbidity, neonatal morbidity, and placental abruption as secondary outcomes. They found the risk of gestational diabetes increased in a stepwise fashion as blood pressure increased, compared with normotensive women. Higher risk of severe maternal and neonatal morbidities was seen only in women with stage 2 hypertension. Placental abruption was rare in this cohort and the odds were not increased in any group.

The findings "highlight the importance of early pregnancy BP elevations, which may reflect prepregnancy BP status," and suggest that the new guidelines "can identify women early in pregnancy who may benefit from increased surveillance," Dr. Sutton and colleagues wrote.

Although randomized trials will be needed to identify the best prevention and management strategies for this patient group, they added, some clinicians may want to consider low-dose aspirin – an intervention shown to safely reduce preeclampsia risk among women with stage 2 hypertension – for women with elevated BP or stage 1 hypertension.

Dr. Sutton and colleagues acknowledged that its retrospective design is among the limitations of their study, and that use of antihypertensive medications could not be captured in their study.

Preeclampsia researcher Mark Santillan, MD, PhD, of the University of Iowa in Iowa City, said in an interview that the results "open the door to considering these new blood pressure categories as a prognosticator" for preeclampsia. "This paper furthers the field by applying these new categories to hypertensive diseases in pregnancy which are not well studied" in comparison to nonpregnant hypertensive states.

"Are these seemingly normal blood pressures associated with poor outcomes, maternal or neonatal? I think that this paper strongly tells us yes," Dr. Santillan added. "But does that mean we have to do more aggressive blood pressure monitoring, seeing your doctor every month or so? Maybe we should change the way we're treating people early on in gestation."

The question of whether aspirin helps reduce preeclampsia risk in women with elevated blood pressure or stage 1 hypertension needs to be resolved in studies, Dr. Santillan said. But because of its favorable risk profile, "if I consider that if a patient has significant risk factors for developing preeclampsia, baby aspirin is fine."

Postpregnancy blood pressure management is something that should also be reconsidered in light of the findings, Dr. Santillan said. Half of women with preeclampsia will have chronic hypertension after they deliver, increasing their risk of adverse cardiovascular outcomes later in life. But because most are young and otherwise healthy, they often are lost to follow-up.

"I think this paper has helped open up that conversation, that there is probably a link between what we're doing in pregnancy to what we should be doing in the postpartum period," he said.

Dr. Sutton and colleagues' study received funding from the Richard King Mellon Foundation, the American Heart Association; and the National Institutes of Health. None of its authors had relevant disclosures. Dr. Santillan disclosed holding U.S. and international patents for preeclampsia prediction, diagnosis, and treatment.

SOURCE: Sutton et al. Obstet Gynecol. 2020;136:129-39.

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