In a study of more than 2,400 women without a history of blood pressure problems, about one in ten were diagnosed with high blood pressure in the year after giving birth, according to a research article published today in Hypertension, a journal of the American Heart Association. Nearly one-fourth of the women were identified have developed postpartum hypertension more than six weeks after delivery, a period during which many women have stopped getting follow-up treatment.
“The findings of our study have implications for postpartum care, particularly among women without a history of high blood pressure,” says lead study author Samantha Parker. “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.”
Postpartum hypertension, or high blood pressure after giving birth, is normally identified within six weeks of delivery, either right away or during the woman’s final postpartum clinic visit, which usually occurs four to six weeks following delivery. Most studies have only measured blood pressure during delivery or hospitalization, which only includes the first few days after birth and only catches the most severe cases.
Postpartum hypertension can have life-threatening side effects include stroke, heart failure, kidney failure, and others in extreme circumstances. And while it is generally known that women who have high blood pressure before or during pregnancy are at risk for cardiovascular disease in later life, relatively few studies have examined the risk for women who experience new-onset hypertension, or high blood pressure for the first time, after giving birth.
Knowing more about high blood pressure after six weeks of postpartum life could help explain the troubling racial differences in maternal health, according to Parker. “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.”
The goal of the study was to find out how common new-onset postpartum hypertension is among people of different races. In order for healthcare providers to recognize pregnant individuals at danger, the researchers also sought to identify contributory factors. At Boston Medical Center, a sizable, major, urban safety-net hospital in Boston, 8,374 deliveries with a pregnancy length of at least 20 weeks from 2016 to 2018 were examined by researchers. Patients in safety-net hospitals are more likely to be uninsured, rely on Medicaid for medical coverage, and have a higher share of poor household incomes.
The 2,465 women in the sample who had no history of chronic high blood pressure or pregnancy-related hypertension were examined for their risk of high blood pressure. Participants were 18 years of age or older, described as non-Hispanic Black 54%, Hispanic or Latino 18%, and had all undergone prenatal treatment and given birth at the same hospital. In addition to demographic and reproductive information from medical records, weight and pre-existing conditions such as Type 2 or gestational diabetes were analyzed.
For the purposes of the study, new-onset postpartum high blood pressure was defined as having a systolic blood pressure of 140 mm Hg or higher and/or a diastolic blood pressure of 90 mm Hg or higher. A systolic blood pressure of 160 mm Hg or higher and/or a diastolic blood pressure of 110 mm Hg or higher were considered to be severe high blood pressure. At least 48 hours after delivery, blood pressure readings were taken, and for the first year following delivery, further readings were gathered from hospital records. After delivery, the majority of the patients (91%) received at least one clinical visit during which their blood pressure was checked.
The time of the diagnosis of hypertension was also studied, along with risk variables both alone and collectively. The data evaluation revealed:
In the year following birth, 298 women (12.1%) who had no prior history of high blood pressure developed the condition.
Although 22% of instances were discovered more than six weeks after delivery, the majority of postpartum high blood pressure diagnosis happened soon after delivery.
Women 35 years of age or older, cesarean deliveries, and current or previous cigarette smoking were risk factors for new-onset postpartum high blood pressure.
The probability of developing new-onset postpartum high blood pressure was 29% for women with all three risk factors, and it was increased to 36% for women who also self-identified as non-Hispanic Black.
The study points out that identifying women with newly-onset postpartum high blood pressure requires a systematic method in order to establish best treatment practices for a racially and ethnically varied group.
Future studies should focus on understanding the negative effects of postpartum hypertension, including hospital readmissions, difficulties during subsequent pregnancies, and cardiovascular disease, the researchers say. Additionally, addressing disparities in maternal cardiovascular disease and death for women of color requires an awareness of the link between pregnancy and hypertension, according to Dr. Parker.
The study’s limitations include the fact that it was a single-center study, and the findings may not be generalizable to other locations or pregnant women under the age of 18. Since there was no strategy for proactively gathering blood pressure measurements for the analysis, data came from electronic medical records of routine office visits. As a result, variables including inconsistent timing and frequency of measurements may have affected the results. Additionally, blood pressure readings taken at clinics may not accurately reflect the “true” average blood pressure of a patient because some people show much higher or lower readings during office visits, which may not be representative of their usual blood pressure.
Source: 10.1161/HYPERTENSIONAHA.122.19275
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