What are the management options for hypertension in pregnancy?

Management of Hypertension in Pregnancy

Antihypertensive therapy should be initiated in pregnant women with blood pressure ≥140/90 mmHg, with methyldopa, labetalol, or nifedipine as first-line agents, while ACE inhibitors and ARBs are strictly contraindicated due to fetotoxicity. 1, 2

Classification of Hypertensive Disorders in Pregnancy

Hypertension in pregnancy is defined as systolic BP ≥140 mmHg and/or diastolic BP ≥90 mmHg, and can be classified into:

1. Pre-existing (chronic) hypertension: Present before pregnancy or diagnosed before 20 weeks gestation
2. Gestational hypertension: Develops after 20 weeks gestation without proteinuria
3. Pre-eclampsia: Gestational hypertension with proteinuria (≥0.3 g/day or ACR ≥30 mg/mmol) or other maternal organ dysfunction
4. Pre-existing hypertension with superimposed gestational hypertension with proteinuria
5. Antenatally unclassifiable hypertension: When BP is first recorded after 20 weeks 1

Diagnostic Approach

• Confirm hypertension with at least two separate measurements (at least 15 minutes apart for severe hypertension)
• Screen for proteinuria in all pregnant women with hypertension using:
  • Dipstick test (if ≥1+, proceed to quantitative assessment)
  • Albumin-to-creatinine ratio (ACR) ≥30 mg/mmol or 24-hour urine collection >0.3 g/day confirms significant proteinuria
• Consider soluble fms-like tyrosine kinase (sFlt)-to-placental growth factor (PlGF) ratio ≤38 to exclude pre-eclampsia development in the next week 1

Treatment Thresholds and Targets

1. Mild to moderate hypertension:

   • Initiate antihypertensive treatment at BP ≥140/90 mmHg in women with:
     • Gestational hypertension (with or without proteinuria)
     • Pre-existing hypertension with superimposed gestational hypertension
     • Hypertension with organ damage or symptoms 1, 2
   • For other pregnant women, initiate treatment at BP ≥150/95 mmHg 1, 3
   • Target BP: <140/90 mmHg but not below 80 mmHg diastolic 2

2. Severe hypertension (BP ≥160/110 mmHg):

   • Considered a medical emergency requiring immediate hospitalization
   • Target BP: <160/110 mmHg but not lower than 130/90 mmHg to avoid compromising uteroplacental perfusion 1, 2

First-Line Pharmacological Management

Mild to Moderate Hypertension

• Methyldopa: 250-500 mg divided twice daily or more frequently

  • Advantages: Long-term safety data available
  • Disadvantages: Sedation, depression 1, 2

• Labetalol: 200-800 mg divided twice daily or more frequently

  • Advantages: Comparable efficacy to methyldopa with fewer side effects
  • Caution: Avoid in asthma 1, 2

• Calcium channel blockers:

  • Nifedipine XR: 30-60 mg once daily
  • Amlodipine: 5-10 mg once daily 2

Severe Hypertension (Emergency)

• IV Labetalol: First-line option
• Oral Nifedipine: Shown to be superior to hydralazine (OR 4.13) 4
• IV Hydralazine: Consider, but associated with more perinatal adverse effects 1
• IV Nitroglycerin: Drug of choice in pre-eclampsia with pulmonary edema 1

Contraindicated Medications

• Absolutely contraindicated:

  • ACE inhibitors
  • Angiotensin II receptor blockers (ARBs)
  • Direct renin inhibitors
  • These medications cause severe fetotoxicity, particularly in second and third trimesters 1, 2

• Use with caution:

  • Atenolol: Associated with fetal growth retardation 1, 2
  • Diuretics: Not first-line agents but probably safe 2

Non-Pharmacological Management

• Recommended for pregnant women with BP 140-149/90-99 mmHg
• Close supervision and limitation of activities
• Normal diet without salt restriction (salt restriction may reduce intravascular volume)
• Regular exercise with caution
• For obese women:
  • Avoid weight gain >6.8 kg during pregnancy
  • Weight reduction not recommended during pregnancy 1

Prevention of Pre-eclampsia

• First-trimester screening for pre-eclampsia risk is recommended for all pregnant women
• Low-dose aspirin (75-100 mg/day) is recommended prophylactically for women with history of early-onset (<28 weeks) pre-eclampsia
  • Start before 16 weeks gestation and continue until delivery 1

Delivery Planning and Postpartum Management

• For pre-eclampsia, induction of labor should be attained after 37 weeks gestation 1
• Continue antihypertensive treatment postpartum if needed
• Monitor closely for 24-72 hours postpartum as hypertension may worsen between days 3-6
• Women with history of pre-eclampsia should have follow-up within 1 week if still requiring antihypertensives at discharge 2

Long-Term Cardiovascular Risk

• Women with history of hypertensive disorders in pregnancy, particularly pre-eclampsia, have:
  • Nearly four times higher risk of developing hypertension later in life
  • More than double the risk of ischemic heart disease
  • Increased risk of stroke and diabetes mellitus 2, 5
• These women require long-term cardiovascular risk monitoring 2

Common Pitfalls to Avoid

• Failing to distinguish between different types of hypertensive disorders in pregnancy
• Using ACE inhibitors or ARBs at any stage of pregnancy
• Lowering BP too aggressively (below 130/90 mmHg), which may compromise uteroplacental perfusion
• Overlooking postpartum hypertension (10% of maternal deaths due to hypertensive disorders occur postpartum) 1
• Missing the opportunity for prevention with aspirin in high-risk women
• Neglecting long-term cardiovascular risk follow-up in women with history of hypertensive disorders in pregnancy