Chronic Hypertension in Pregnancy – Evaluation and Management

CLINICAL ACTIONS:

ACOG has released recommendations on chronic hypertension in pregnancy. Management of chronic hypertension in pregnancy depends on gestational age and symptoms. Initial assessment, including identification of end-organ damage and evaluation of medications will drive treatment and delivery planning.

• Evaluation
• Medical Management
• Fetal Surveillance
• Timing of Delivery
• Postpartum

Evaluation

• Ideally preconception or the first prenatal visit is the optimal time to establish a diagnosis (primary vs. secondary hypertension) and assess for end-organ damage, based on a thorough history and physical

Laboratory tests

• Complete blood count
• Liver function tests
• Serum electrolytes (esp. potassium)
• Renal Function Tests
  • Serum creatinine
    • Mild renal impairment: Cr 0.9-1.4
    • Moderate renal impairment: Cr 1.4-2.4
    • Severe renal impairment: Cr 2.4-2.8
  • Blood urea nitrogen
  • Spot urine protein/creatinine to screen for proteinuria
    • <0.15 denotes patient spilling <300 mg for a 24-hour sample
    • If spot urine ratio elevated, do 24-hour urine
    • Note: 24-hour urine assessment not required if normal Cr and spot urine ratio <0.15
  • Order ECG if ≥1 of the following
    • Chronic hypertension present >4 years
    • Maternal age >30 years with long standing hypertension
    • History abnormal ECG
    • Additional risk factors (i.e. long-standing diabetes)

SYNOPSIS:

The benefits of treating mild to moderate chronic hypertension in pregnancy are not clear, thus a conversation with patients (i.e. shared decision-making) is warranted. Timing of delivery depends on severity of disease and gestational age. Women with chronic hypertension remain at risk for complications during the postpartum period so early follow-up is recommended.

KEY POINTS:

Medical Management

Choice of Antihypertensive

• Most commonly used antihypertensives
  • Labetalol – ‘preferred’: 200 to 2,400 mg/d po (2 to 3 divided doses)
    • Initiate at 100 to 200 mg twice a day
    • Watch for potential bronchospasm
    • Avoid in women with asthma, heart disease, congestive heart failure, bradycardia and heart block
  • Nifedipine – ‘preferred’: 30 to 120 mg/d po (avoid sublingual)
    • Initiate at 30 to 60 mg daily (extended release)
    • Avoid in women with tachycardia
  • Methyldopa – ‘less favored’: 500 to 3,000 mg/d po (2 to 4 divided doses)
    • Initiate at 250 mg twice or 3 times/day
    • May not be as effective and limited by side-effects such as dizziness, depression or sedation
  • Second line therapy
    • HCTZ (considered a safe diuretic)
  • Other medications are available and may be used with MFM consultation
  • Note: The following medications are not recommended
    • Ace inhibitors | Angiotensin II receptor blockers | Renin inhibitors | Mineralocorticoid receptor antagonists | Atenolol (due to risk for FGR and LBW)

Threshold for Initiation of therapy  

• Based on the CHAP Trial (see ‘Related ObG Entries’ below), ACOG and SMFM have revised guidance regarding initiation of therapy for women with mild chronic hypertension during pregnancy 
• Start antihypertensive therapy at >140/90 

Patient on medications prior to pregnancy

• In the absence of mitigating factors or side effects
  • Maintain on their medications
  • Do not discontinue and wait until blood pressures in the severe range to initiate therapy
  • Individualize decision whether to discontinue
• Replace contraindicated medications and monitor therapy and BP targets accordingly

Target BP

• ACOG
  • Notes that RCT (CHAP Trial) demonstrated benefit of using 140/90 as threshold but did not determine ideal target BP or if there is a BP at which growth restriction may be a concern
• SMFM
  • “…recommends treatment with antihypertensive therapy for mild chronic hypertension in pregnancy to a goal BP <140/90 mm Hg”

Aspirin

• Use aspirin for risk reduction (see ‘Related ObG Topics below)
  • Initiate daily low dose aspirin (81 mg) between 12 to 28 weeks gestation

Fetal Surveillance

• Antepartum
  • Timing/interval of testing not well established
  • Assess fetal growth in the 3^rd trimester
• Intrapartum
  • Continuous fetal monitoring

Timing of Delivery

• Chronic HTN and no medications
  • Delivery <38w0d not recommended
• Chronic HTN well controlled on maintenance antihypertensive medication
  • Delivery <37w0d not recommended
• Chronic HTN with superimposed preeclampsia without severe features
  • Expectant management with delivery at 37w0d
• Chronic HTN with superimposed preeclampsia with severe features
  • Expectant management under certain circumstances until delivery at 34w0d (inpatient care only)
  • Initiation of antenatal steroids as per guidelines (see ‘Related ObG Topics below)
• Note: When considering the latest time to deliver, ACOG states

…expectant management beyond 39 0/7 weeks of gestation should only be done after careful consideration of the risks and benefits and with appropriate surveillance

Postpartum

• Early ambulatory visits (within 2 weeks) postpartum
  • Severe HTN or superimposed preeclampsia may develop for the first time in the postpartum period
• Patient may return to prepregnancy regimen and managed appropriately, without fetal considerations
  • Note: Avoid methyldopa in postpartum period due to risk for depression
• Careful medication titration to achieve BP no higher than 150/100 mm Hg
• Analgesia
  • NSAIDs were not associated with BP elevation based on data from women with preeclampsia with severe features
• Breastfeeding
  • Antihypertensives can be used in breastfeeding women
  • Propranolol and labetalol are preferred due to lower levels in breast milk compared to some other medications
  • ACE inhibitors can also be used safely unless high doses required
  • Calcium channel blockers are not associated with adverse outcomes
  • Note: Diuretics may reduce quantity of breast milk

Learn More – Primary Sources:

ACOG Practice Bulletin 203: Chronic Hypertension in Pregnancy

ACOG: Clinical Guidance for the Integration of the Findings of the Chronic Hypertension and Pregnancy (CHAP) Study

SMFM Statement: Antihypertensive therapy for mild chronic hypertension in pregnancy (The CHAP Trial)

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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