Study: Surprising Number of Postpartum Hypertension Cases Occurred More than 6 Weeks After Birth

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De novo postpartum hypertension (dn-PPHTN) occurred in 1 of 10 patients in the year after delivery, with nearly a quarter of diagnoses made more than 6 weeks after birth, according to new data from a large urban safety-net hospital published in Hypertension.

“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, assistant professor of epidemiology, Boston University School of Public Health, in a press release.“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.”

Parker and colleagues conducted a retrospective cohort study of 3925 deliveries from 2016 to 2018 at a large urban safety-net hospital in Boston, assessing all blood pressure (BP) measures during pregnancy through 12 months postpartum. Women with chronic HTN or hypertensive disorders of pregnancy were excluded. Within the cohort, 54% of the women were non-Hispanic Black and 18% were Hispanic.

“Understanding more about high blood pressure beyond 6 weeks after delivery may provide insight into the alarming racial disparities in maternal health,” said Parker in the release. “Previous research has shown that new-onset hypertension after childbirth may be up to 2.5 times more common among non-Hispanic Black women compared to white women.”

For the purpose of the study, dn-PPHTN was defined as 2 separate BP readings with systolic BP BP ≥140 mm Hg and diastolic BP ≥90 mm Hg at least 48 hours after delivery. Severe dn-PPHTN was defined as systolic BP ≥160 and diastolic BP ≥110. Investigators examined risk factors individually and in combination and timing of diagnosis.

In the final cohort of 2465 women without a history of HTN, 12.1% developed dn-PPHTN,17.1% of whom had severe dn-PPHTN, according to researchers.

Compared to women without dn-PPHTN, those who developed dn-PPHTN were more likely to be aged ≥35 years, be non-Hispanic Black, deliver via cesarean, or be current or former smokers. Patients with all these characteristics had a 29% risk of developing dn-PPHTN, which was higher among Black patients (36%). Approximately 22% of dn-PPHTN cases were diagnosed after 6 weeks postpartum, according to researchers.

“Opportunities to monitor and manage patients at the highest risk of dn-PPHTN throughout the entire year postpartum could mitigate cardiovascular related maternal morbidity,” concluded Parker et al.

The team noted that future research should focus on understanding adverse outcomes associated with dn-PPHTN, such as hospital readmissions, subsequent pregnancy complications, and cardiovascular disease.

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

Study limitations include its single-center design and use of data from electronic health records of standard office visits, inconsistency in which may have led to variability in the study analysis. Also, clinic BP measurements may not reflect true average BP.

Reference: Parker SE, Ajayi A, Yarrington CD. De novo postpartum hypertension: Incidence and risk factors at a safety-net hospital. Hypertension. Published online November 15, 2022. doi: 10.1161/HYPERTENSIONAHA.122.19275.