High BP hits one in eight women after childbirth

Hypertension is common after childbirth but may be undetected due to limited follow-up, researchers say.

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One in eight women may develop high blood pressure in the year after childbirth, US research has found.

Among these women with new-onset hypertension, more than one in five developed hypertension more than six weeks after delivery, suggesting many cases go undetected as postpartum follow up typically does not extend beyond that.

According to the analysis of 2400 women who delivered at a Boston hospital, mothers who were older (35 or over), who had a caesarean delivery or who had any history of smoking were more likely to develop hypertension for the first time in the 12 months post-delivery.

In fact, if they had all three risk factors, they had a 30% chance of developing the condition, according to the study in Hypertension.

The findings had implications for postpartum care, particularly among women without a history of high blood pressure, said lead author and epidemiologist Dr 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,” Dr Parker said in a statement.

“Monitoring during this period could mitigate severe postpartum and long-term cardiovascular complications.”

None of the women included in the study had a history of hypertension.

The researchers found that 12% of those women developed hypertension for the first time in that year, and 17% of that sub-group had severe hypertension.

While most cases of hypertension were diagnosed during the delivery hospital stay, 22% were diagnosed more than six weeks after delivery.

The authors defined de novo postpartum hypertension as two separate blood pressure readings of 140/90mmHg at least 48 hours after delivery. Severe postpartum hypertension was defined as 160/110mmHg.

In an accompanying editorial, the authors noted that around 8% of women of reproductive age females had chronic hypertension, and 2% to 8% of pregnancies were complicated by gestational hypertension or preeclampsia.

“Excluding de novo postpartum hypertension, nearly one in 10 pregnancies is complicated by hypertension,” the authors said.

“Once de novo postpartum hypertension is included, up to one in five pregnant people experience a hypertensive disorder. Pregnancy-associated hypertension should thus be viewed as a top public health priority.

“The findings … beg the question: is pregnancy a stress test, a risk factor or both?”

These authors raised the concern that the study may have simply captured patients with previously undetected hypertension before pregnancy.

“Systemic vascular resistance decreases in the first trimester of pregnancy and BPs may be up to 30% lower than baseline in the second trimester. However, when the study population was restricted to the 1392 patients who entered prenatal care at 13 weeks’ gestation, the de novo postpartum hypertension rate was similar at 13.3%, strengthening the credibility of the authors’ findings.”

Hypertension 2022, online 15 November