Many Cases of New-Onset Postpartum Hypertension Go Unnoticed for Weeks

Samantha Parker, PhD

An analysis of deliveries occurring at the Boston Medical Center from 2016-2018 is providing clinicians with new insights into the risk of new-onset postpartum hypertension.

A look at more than 8300 deliveries with a pregnancy length of at least 20 weeks, the study identified being aged 35 years or older, delivery via cesarean, or being a current or former cigarette smoker as risk factors for new-onset postpartum hypertension and produced evidence suggesting more than 1-in-10 with no prior history went on to develop hypertension in the year following delivery.

“The findings of our study have implications for postpartum care, particularly among women without a history of high blood pressure,” said lead study author Samantha Parker, PhD, an assistant professor of epidemiology at Boston University School of Public Health, in a statement from the American Heart Association. “We were surprised at the number of cases captured more than six weeks after delivery, a period that falls well outside of routine postpartum follow-up. Monitoring during this period could mitigate severe postpartum and long-term cardiovascular complications.”

With a renewed emphasis on cardio-obstetrics in recent years, research efforts have begun to further explore associations of hypertensive disorders of pregnancy with negative cardiovascular outcomes. However, fewer research endeavors have examined incidence and risk factors of new-onset postpartum hypertension, also known as de novo postpartum hypertension (dn-PPHTN) using contemporary data. With this in mind, Parker, along with colleagues Ayodele Ajayi, MBBS, MPH, and Christina Yarrington, MD, of Boston University, designed a retrospective medical record-based cohort study of deliveries occurring at the Boston Medical Center, a large, central, urban safety-net hospital.

Limiting their analyses to pregnancies among adult patients of at least 20 weeks in length from 2016-2018, investigators identified 3925 deliveries for potential inclusion in their analyses. Further restricting this population to those without chronic hypertension or hypertensive disorders of pregnancy, investigators identified 2465 patients without a history of hypertension for inclusion. Using this cohort, investigators planned to assess for dn-PPHTN within 1 year of delivery, which was defined as 2 separate blood pressure reading with a systolic blood pressure at or exceeding 140 mmHg and a diastolic blood pressure at or exceeding 90 mmHg at least 48 hours after delivery. Secondary outcomes of interest included risk factors individually and in combination as well as timing of diagnosis and occurrence of severe dn-PPHTN, a systolic blood pressure at or exceeding 160 mmHg and a diastolic blood pressure at or exceeding 110 mmHg.

Among the 2465 patients included in the study, 12.1% (n=298) developed dn-PPHTN during the first year following delivery. Among this group of patients, 17.1% (n=51) developed severe dn-PPHTN. An analysis of patient characteristics among those who developed dn-PPHTN compared to those who did not were more likely to be 35 years or older (36.2% vs 22.8%), delivered via cesarean, or be current or former smoker, with patients with all of these characteristics at a 29% risk of developing dn-PPHTN. Investigators noted this increase in risk was even more apparent in non-Hispanic Black patients (36%). Investigators pointed out 22% cases were diagnosed 6 weeks or more postpartum.

“Understanding the relationship between pregnancy and hypertension is particularly important in addressing inequities in maternal cardiovascular disease and death for people of color,” Parker added.

This study, “De Novo Postpartum Hypertension: Incidence and Risk Factors at a Safety-Net Hospital,” was published in Hypertension.