An analysis of more than 2,400 women who did not have high blood pressure while pregnant found that approximately 1 in 10 were diagnosed with high blood pressure during the year following childbirth.  Twelve percent of women with normal blood pressure (BP) during pregnancy experienced new-onset postpartum hypertension in the year after delivery, according to a study published in a recent issue of the American Heart Association journal Hypertension.

Postpartum hypertension is more likely to follow a pregnancy complicated by hypertension, but new-onset hypertension—or “de novo postpartum hypertension (dn-PPHTN)”—also may follow a normotensive pregnancy, the study authors state.  In this study, nearly a quarter of the women were diagnosed more than 6 weeks after delivery—a timeframe during which many women have stopped receiving follow-up care.

Expanding the knowledge base

Postpartum hypertension is typically discovered within 6 weeks of delivery—either immediately after childbirth or during a woman’s final postpartum clinic visit conducted at 4 to 6 weeks after delivery.  Data is limited for the time beyond 6 weeks since most prior studies have relied on blood pressure measurements taken during delivery or hospitalization, which includes just the first few days postpartum and captures only the most severe cases.

In severe cases, postpartum hypertension is associated with life-threatening complications, including stroke, heart failure, kidney failure, and more.  And, while it is well established that women with high blood pressure before or during pregnancy are at risk for cardiovascular disease later in life, few studies to date have assessed cardiovascular risk for women who develop high blood pressure for the first time—or new-onset hypertension—following childbirth.

Study specifics

This observational study conducted by researchers at the Boston University School of Public Health sought to estimate the incidence of and identify risk factors for dn-PPHTN in a diverse patient population.  Participants were women aged 18 and older, 54% of whom self-identified as non-Hispanic Black, and 18% of whom identified as Hispanic or Latino.   All of the study participants received prenatal care and delivered their babies at the same hospital.  The researchers reviewed demographic and reproductive characteristics from medical records in addition to noting weight and pre-existing illnesses such as Type 2 or gestational diabetes.

Using medical record data, the researchers examined the blood pressure measurements of the mothers of 3,925 babies born from 2016 to 2018, from pregnancy through 12 months postpartum.

Among the 2,465 patients without a history of hypertension, 298 (12.1%) developed dn-PPHTN.  Of these women, 17.1% experienced severe dn-PPHTN.

The researchers defined dn-PPHTN as 2 separate readings of systolic BP ≥140 mmHg and diastolic BP ≥90 mmHg experienced at least 48 hours after delivery.  Severe dn-PPHTN was defined as systolic BP ≥160 and diastolic BP ≥110.

While most postpartum high blood pressure diagnoses in the study participants occurred shortly after delivery, approximately 22% of cases of dn-PPHTN were diagnosed more than 6 weeks postpartum.

Risk factors and findings

The women in the study who developed dn-PPHTN were more likely to be 35 or older, current or former smokers, and to have had a cesarean section, the study found.  Patients with all these characteristics had a 29% risk of developing dn-PPHTN.  Among Black women with these characteristics enrolled in the study, the risk rose to 36%.

The investigators contend that determining best care practices for a racially and ethnically diverse population first requires a systematic approach to identifying women with new-onset postpartum high blood pressure.

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

Their research findings “have implications for postpartum care, particularly among patients without a history of hypertension,” stated lead author Samantha Parker, Ph.D., in an accompanying university 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,” she added.  “Monitoring during this period could mitigate severe postpartum and long-term cardiovascular complications.”

A link to obtaining to complete study “De Novo Postpartum Hypertension: Incidence and Risk Factors at a Safety-Net Hospital,” is found at https://pubmed.ncbi.nlm.nih.gov/36377603/

Clinicians’ Bonus:  More To Know

Be sure to review the American Heart Association’s Scientific Statement, “Cardiovascular Considerations in Caring for Pregnant Patients.”

The contents of this feature are not provided or reviewed by NPWH.