Prehypertensive pregnant women also at risk of pre-eclampsia

Pre-eclampsia (PE) and its related adverse outcomes are not limited to pregnant women with blood pressure (BP) >140/90 mm Hg, according to a study. Those with prehypertensive BP may also benefit from closer monitoring.

“However, before implementation, further research is needed to determine whether identification, closer monitoring, and intervention in these women will improve maternal and perinatal outcomes,” the researchers said.

This retrospective study included 18,243 singleton pregnancies at Monash Health, Australia, and obtained data on maternal characteristics and BP measurements at varying gestational ages. BPs were further categorized as (1) mean arterial pressure and (2) normal, elevated, stage 1, and stage 2 hypertension, as per the American College of Cardiology guidelines.

The researchers conducted a multivariable regression analysis to determine relationships between BP categories and pregnancy outcomes.

A positive­ dose–response relationship was identified between mean arterial pressure and the development of PE in later pregnancy. [Am J Obstet Gynecol 2020;222:606.e1-606.e21]

PE risk across all gestational ages was higher in those with elevated BP (adjusted risk ratio [aRR], 2.45, 95 percent confidence interval [CI], 1.74–3.44 at 34–36 weeks’ gestation) and stage 1 hypertension (aRR, 6.60, 95 percent CI, 4.98–8.73 at 34–36 weeks’ gestation) as compared with those with normal BP. Of note, stage 1 hypertension was associated with preterm birth and adverse perinatal outcomes.

Several studies have shown that prehypertension in the first and second trimester may lead to a higher incidence of PE. A prospective study of 2,947 women further demonstrated that stage 1 hypertension correlated with a two- to threefold increased PE risk compared with the normotensive group. [Circ Res 2019;125:184-194; Obstet Gynecol 2018;132:843-849; Am J Obstet Gynecol 2019;221:277.e1-277.e8]

Furthermore, these findings suggest that BP ≥140/90 mm Hg may not be the “ideal threshold” for determining women at risk of hypertensive disorders of pregnancy. Additionally, the Hyperglycemia and Adverse Pregnancy Outcomes study found a continuous relationship between glycaemic levels and adverse pregnancy outcomes. [N Engl J Med 2008;35:1991-2002]

“This landmark study has steered changes to pregnancy guidelines, which now recommend lower glucose thresholds for the diagnosis of gestational diabetes, thus identifying a broader group of women who are at risk of the associated adverse events,” the researchers said.

“However, these guidelines have not been adopted by the American society due to lacking evidence that intervention at lower glycaemic levels improves pregnancy outcomes,” they added.

The researchers also stressed that BP “does not exist in isolation.” As such, other risk factors must be considered when screening women for PE.

“The poor predictive value of BP alone is highlighted by our study, as the majority of women with elevated, stage 1 and stage 2 hypertension do not develop PE or the associated adverse outcomes,” they said. “Perhaps, a multifactorial risk assessment is more appropriate for the prediction of PE and adverse outcomes rather than BP alone.”