Chronic Hypertension in Pregnancy: Diagnosis and BP Measurement

SUMMARY:

The ACOG guidance on chronic hypertension in pregnancy addresses diagnosis, particularly in light of the 2017 ACC/AHA recommendations that lowered the BP thresholds (see ‘Related ObG Topics’, below). ACOG states that for patients with stage 1 hypertension (systolic blood pressure of 130–139 mm Hg or diastolic blood pressure of 80–89 mm Hg) 

…it is reasonable to continue to manage the patient in pregnancy as chronically hypertensive as specified in this guideline.

The uncertainty of the new approach to hypertension recommended by the ACA and AHA as applied to the care of pregnant women should be an active area of investigation.

Chronic Hypertension: Definitions and Criteria   

  • Definition: Hypertension that is  
    • Diagnosed or present before pregnancy or before 20 weeks of gestation 
    • Diagnosed for the first time during pregnancy without resolution postpartum 
    • Note: ACOG states that “the 20-week convention should not be used dogmatically, but rather for orientation while maintaining clinical judgment.” 
  • Traditional criteria  
    • Systolic BP: ≥140 mm Hg  and/or
    • Diastolic BP: ≥90 mm Hg  
    • ≥2 determinations at least 4 hours apart 
    • Note: In the context of severe hypertension, “the diagnosis can be confirmed within a shorter interval (even minutes) to facilitate timely therapy” 
  • ACC/AHA criteria and definition  
    • Lower threshold (see above) may result in false positive assignment of chronic hypertension  

Superimposed Preeclampsia 

  • Preeclampsia that “complicates preexisting chronic hypertension”  
    • May occur in up to 50% of women with chronic hypertension or higher with end-organ failure  
  • Risk increased in the following 
    • African American | Obesity | Smoker | Hypertension ≥4 years | DBP >100 mm Hg at baseline | Previous history of preeclampsia  
  • Consider diagnosis in the following clinical scenarios 
    • Sudden increase in BP or 
    • Proteinuria (above threshold or patient baseline)  
    • Thrombocytopenia | Abnormal LFTs | Elevated Uric Acid  
  • Consider referral to MFM

BP Measurements 

  • Avoid caffeine and smoking prior to taking measurements (minimum 30 minutes)  
  • Cuff size should  
    • Be 1.5 times upper arm circumference or 
    • Encircle arm by at least 80% of the arm width | at last 40% arm circumference  
    • Arm should be at level of the heart  
  • Repeat measurements at a minimum 10 minutes apart  
  • Patient should be seated, legs uncrossed and back supported

Key Points:

  • Distinction between chronic hypertension and gestational hypertension/preeclampsia can be difficult in the following clinical scenarios 
    • Patient enters care after 20 weeks 
    • Patients with chronic hypertension may have proteinuria due to nephropathy 
    • BP in pregnant women can drop for physiologic reasons, rebounding to pregestational levels later in pregnancy  
    • Acceptable time for resolution of hypertension postpartum not well established  
  • ACOG addresses out-of-office and self-monitoring of BP  
    • Advantages include patient convenience and adherence  
    • Procedures should include 
      • Patient education | Ensure device validation   
    • Home devices can be compared to office devices to ensure accuracy

Learn More – Primary Sources:  

ACOG Practice Bulletin 203: Chronic Hypertension in Pregnancy

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