Stage 2 hypertension increases risk for maternal, fetal, neonatal adverse outcomes

Bone reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.

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Severe stage 2 hypertension, but not elevated BP and stage 1 hypertension, was associated with maternal, fetal or neonatal mortality or morbidity in low-resource settings, according to new research published in The Lancet Global Health.

“Nearly all evidence for using the American College of Cardiology and American Heart Association thresholds to diagnose hypertension in pregnancy are from high-income settings and rely on retrospective, routinely collected clinical data. Furthermore, these studies have focused exclusively on associative measures (such as risk ratios) between blood pressure thresholds and adverse outcomes,” Jeffrey N. Bone, MSc, from the department of obstetrics and gynecology at BC Children’s Hospital Research Institute in Vancouver, British Columbia, Canada, and colleagues wrote. “By contrast, this study provides prospective blood pressure data from more than 20,000 pregnant women, in three low-income and middle-income countries, using standardized measurement technique and a validated device, and examines not only associations between blood pressure thresholds and adverse outcomes, but also the diagnostic test properties of those thresholds.”

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Researchers conducted a secondary analysis of data from pregnant women identified by trained community health workers from the Community-Level Interventions for Preeclampsia (CLIP) cluster randomized trials in India (n = 6,067), Mozambique (n = 4,163) and Pakistan (n = 10,839) from November 2014 to February 2017. All women had data on BP measurements and outcomes.

Women were classified according to their maximum BP measurement category of:

  • normal BP (systolic BP, < 120 mm Hg and diastolic BP, < 80 mm Hg);
  • elevated BP (systolic BP, 120 mm Hg to 129 mm Hg and diastolic BP, < 80 mm Hg);
  • stage 1 hypertension (systolic BP, 130 mm Hg to 139 mm Hg or diastolic BP, 80 mm Hg to 89 mm Hg or both);
  • nonsevere stage 2 hypertension (systolic BP, 140 mm Hg to 159 mm Hg or diastolic BP, 90 mm Hg to 109 mm Hg or both); or
  • severe stage 2 hypertension (systolic BP, 160 mm Hg or diastolic BP, 110 mm Hg or both).

The primary outcome was a maternal, fetal or neonatal mortality or morbidity adverse outcome.

Among the 21,069 pregnant women analyzed, 10.4% had elevated BP, 17.8% had nonsevere stage 1 hypertension and 6.4% had nonsevere or severe stage 2 hypertension. Compared with women with normal BP, women with nonsevere or severe stage 2 hypertension experienced more maternal (RR for nonsevere = 1.2; 95% CI, 0.9-1.59; RR for severe = 2.4; 95% CI, 1.6-3.59), fetal or neonatal (RR for nonsevere = 1.48; 95% CI, 1.1-1.97; RR for severe = 4.09; 95% CI, 3.02-5.55) adverse outcomes.

Researchers observed dose-response relationships between increasing BP thresholds and all adverse outcomes among women with any higher BP category compared with women with BP in lower categories. However, likelihood ratios were only informative among women with severe stage 2 hypertension and maternal adverse outcomes (likelihood ratio = 6.36; 95% CI, 3.65-11.07) and perinatal death (likelihood ratio = 5.07; 95% CI, 2.64-7.07), especially with stillbirth (likelihood ratio = 8.53; 95% CI, 5.63-12.92).

“Antenatal care must aim to provide more than accurate blood pressure measurement to achieve the Countdown 2030 goals,” the researchers wrote.