What is the treatment for Pregnancy-Induced Hypertension (PIH)?

Treatment of Pregnancy-Induced Hypertension (PIH)

The first-line pharmacological treatment for pregnancy-induced hypertension is methyldopa, nifedipine, and/or labetalol, with the goal of maintaining blood pressure between 110-140/85 mm Hg to prevent progression to severe hypertension. 1

Classification and Diagnosis

PIH is defined as systolic blood pressure (SBP) >140 mmHg and diastolic blood pressure (DBP) >90 mmHg during pregnancy and can be classified as:

• Mild: SBP 140-149 and DBP 90-99 mmHg
• Moderate: SBP 150-159 and DBP 100-109 mmHg
• Severe: SBP ≥160 and DBP ≥110 mmHg 2

PIH encompasses:

1. Pre-existing hypertension
2. Gestational hypertension and preeclampsia
3. Pre-existing hypertension with superimposed gestational hypertension with proteinuria
4. Unclassifiable hypertension 2

Pharmacological Management

First-Line Medications

• Methyldopa: Drug of choice during pregnancy 2
• Nifedipine: Extended-release formulation, effective after 20 weeks gestation 3
• Labetalol: Efficacy comparable to methyldopa 2

Treatment Thresholds

• Initiate antihypertensive treatment when BP ≥150/95 mmHg according to ESH/ESC guidelines 2
• Consider treatment at BP ≥140/90 mmHg in women with:
  • Gestational hypertension (with or without proteinuria)
  • Pre-existing hypertension with superimposed gestational hypertension
  • Hypertension with asymptomatic organ damage or symptoms 2

Contraindicated Medications

• ACE inhibitors, ARBs, and direct renin inhibitors are strictly contraindicated during pregnancy due to fetotoxicity 1, 2

Management Algorithm

1. For mild hypertension (140-149/90-99 mmHg):

   • Consider non-pharmacological management with close monitoring 2
   • If treatment needed, start with methyldopa 250-500 mg 2-4 times daily 4

2. For moderate hypertension (150-159/100-109 mmHg):

   • Start methyldopa or labetalol or extended-release nifedipine
   • Methyldopa: 250-500 mg 2-4 times daily
   • Labetalol: 100-400 mg twice daily
   • Nifedipine XR: 30-60 mg once daily 1, 5

3. For severe hypertension (≥160/110 mmHg):

   • Immediate hospitalization and treatment within 30-60 minutes 6
   • IV medications may be required (hydralazine, labetalol) 3
   • Consider magnesium sulfate for prevention of eclampsia 1

Magnesium Sulfate Protocol for Preeclampsia

For treatment and prevention of eclampsia, use IV magnesium:

• Loading dose: 4g IV plus 5g IM in each buttock (14g total)
• Maintenance: 5g IM every 4 hours for 24 hours 1

Monitoring and Follow-up

• All women with preeclampsia should be assessed in hospital when first diagnosed
• Some may be managed as outpatients once their condition is stable 1
• Monitor for signs of worsening condition:
  • Repeated episodes of severe hypertension despite treatment
  • Progressive thrombocytopenia
  • Abnormal renal or liver enzyme tests
  • Pulmonary edema
  • Abnormal neurological features
  • Non-reassuring fetal status 1

Timing of Delivery

Consider delivery at gestational age <34 weeks if:

• Repeated episodes of severe hypertension despite treatment with 3 classes of antihypertensives
• Progressive thrombocytopenia
• Progressively abnormal renal or liver enzyme tests
• Pulmonary edema
• Abnormal neurological features
• Non-reassuring fetal status 1

Postpartum Management

• Continue monitoring BP for at least 72 hours in hospital and 7-10 days postpartum 6
• ACE inhibitors like enalapril are first-line treatment for postpartum hypertension in breastfeeding mothers 6
• Calcium channel blockers are effective alternatives 6
• Avoid methyldopa postpartum due to risk of postnatal depression 6

Pitfalls and Caveats

1. Do not use ACE inhibitors or ARBs during pregnancy - they cause severe fetotoxicity 1
2. Do not lower BP too aggressively - maintain between 110-140/85 mm Hg to prevent compromising uteroplacental perfusion 1, 6
3. Be aware of drug interactions - methyldopa may interfere with certain laboratory tests, including urinary catecholamines 4
4. Monitor for maternal and fetal complications - PIH increases risk of abruptio placentae, cerebrovascular events, organ failure, intrauterine growth restriction, and prematurity 2
5. Consider long-term cardiovascular risk - Women with PIH have increased risk of future cardiovascular disease 6