BACKGROUND AND PURPOSE:

• The ACC/ AHA blood pressure guidelines, revised in November 2017, redefine BP categories
  • Stage 1: systolic 130-139mmHg or diastolic 80-89mmHg
  • Elevated: systolic 120-129mmHg and diastolic <80mmHg
  • Normal: <120/<80 mmHg
• Relevance to obstetric population is currently unknown
• Hausburg et al. (AJOG, 2019) evaluated the risk of gestational hypertension or preeclampsia based on BP category and trajectory

METHODS:

• Prospective observational cohort study
• Data set
  • Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be (nuMoM2b)
  • Nulliparous | Singleton pregnancies | No history of pre-pregnancy hypertension (≥140/90 mmHg) or diabetes
• Compared
  • Frequency of hypertensive disorders of pregnancy using ACC/AHA BP category at a first trimester study visit
  • BP trajectory between study visits in the first and second trimesters
• BP trajectories were categorized based on difference between visit 1 and 2 as
  • Stable: <5mmHg difference
  • Upward : ≥5mmHg
  • Downward: ≤-5mmHg
• Data analysis: Associations of BP category and trajectory with
  • Preeclampsia and gestational hypertension
  • Univariate analysis and multinomial logistic regression analysis with co-variates identified a priori to account for confounding

RESULTS:

• 8,899 women were included in the analysis
• Mean gestational age at study visit
  • Study visit 1: 11.6 weeks
  • Study visit 2: 19.0 weeks
• Increasing blood pressure category was associated with a higher risk of all hypertensive disorders
  • Elevated blood pressure: Adusted relative risk (aRR) 1.54 (95%CI, 1.18 to 2.02)
  • Stage 1 hypertension: aRR 2.16 (95%CI, 1.31 to 3.57)
• Stage 1 hypertension was associated with the highest risk of preeclampsia with severe features: aRR 2.48 (95%CI, 1.38-8.74)
• Systolic and diastolic blood pressure trajectories were both significantly associated with the risk of hypertensive disorders independent of blood pressure category (p<0.001)
• Initial BP normal but upward systolic trajectory compared to patients with downward trajectory
  • Risk of any hypertensive disorder: aRR 1.41 (95%CI 1.20-1.65)

CONCLUSION:

• New BP category system was significantly associated with both preeclampsia and gestational hypertension
  • Category 1 hypertension in the first trimester was associated with double the risk for hypertensive disorders in pregnancy
• BP trajectory in early pregnancy was independently associated with risk of preeclampsia and gestational hypertension
  • Initial normal BP but upward systolic trajectory compared to patients with downward trajectory was associated with increased risk of 41% of any hypertensive disorder
• The authors conclude that the new BP guidelines with lower thresholds may identify more women at risk for preeclampsia and gestational hypertension and that more research is needed to determine value of interventions such as low dose aspirin
• Note: This study was done on data derived from nulliparous population

Learn More – Primary Sources:

Blood pressure trajectory and category and risk of hypertensive disorders of pregnancy in nulliparous women

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ACC/AHA Blood Pressure Guideline: New Classification System and Treatment Targets

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