Treatment of Pregnancy-Induced Hypertension
Extended-release nifedipine and labetalol are equally effective first-line antihypertensive medications for pregnancy-induced hypertension, with methyldopa as another acceptable option. 1
Classification and Thresholds for Treatment
Pregnancy-induced hypertension (PIH) is 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
Treatment thresholds:
- For non-severe hypertension: Initiate pharmacotherapy at BP ≥150/95 mmHg 3, 1
- For severe hypertension (≥160/110 mmHg): Consider an emergency requiring immediate treatment 3
First-Line Medications
1. Labetalol
- Dosing: Initial IV dose of 20 mg bolus, followed by 40 mg after 10 minutes if needed, then 80 mg every 10 minutes for 2 additional doses (maximum 220 mg) 3, 1
- Advantages: Increasingly preferred over methyldopa due to reduced side effects 3
- Contraindications: Second or third-degree AV block, maternal systolic heart failure, and history of reactive airway disease/asthma 1
2. Extended-Release Nifedipine
- Advantages: Once-daily dosing improves patient adherence 1
- Caution: Risk of uncontrolled hypotension when combined with magnesium sulfate 1
3. Methyldopa
- Traditional first-line agent with long-term safety data 3
- Dosing: 1-1.5 g orally if IV access is not established 1
- Limitations: May be less well tolerated due to side effect profile 1
Medications to Avoid During Pregnancy
- Absolutely contraindicated: ACE inhibitors, ARBs, direct renin inhibitors, and mineralocorticoid receptor antagonists due to teratogenic effects 3, 1
- Avoid if possible: Atenolol due to risk of fetal growth restriction 3, 1
Treatment Approach Based on Severity
Mild Hypertension (140-149/90-99 mmHg)
- Consider non-pharmacological management including:
- Close supervision and limitation of activities
- Normal diet without salt restriction
- No weight reduction even in obese women 3
Moderate Hypertension (150-159/100-109 mmHg)
- Initiate pharmacotherapy with one of the first-line agents
- Target BP: 140-150/90-100 mmHg (not below 80 mmHg for diastolic) 1
Severe Hypertension (≥160/110 mmHg)
- Requires immediate hospitalization and treatment
- IV labetalol is preferred (dosing as above)
- Alternative options:
Special Considerations
Preeclampsia Management
- Magnesium sulfate is indicated for seizure prophylaxis
- Loading dose: 4 g IV over 5 minutes, followed by maintenance dose of 1 g/hour IV infusion 1
- Continue for at least 24 hours postpartum 1
Monitoring Requirements
- Continuous maternal blood pressure monitoring
- Respiratory rate monitoring
- Deep tendon reflexes assessment
- Urine output monitoring
- Fetal heart rate monitoring 1
- Critical care consultation if BP control not achieved within 360 minutes despite two medications 1
Important Pitfalls to Avoid
Drug interactions: Caution when using nifedipine with magnesium sulfate due to risk of precipitous BP drop 3
Laboratory interference: Methyldopa may cause false positive results in screening tests for pheochromocytoma 4
Fetal monitoring: Monitor fetal heart rate during uptitration of labetalol, especially when doses exceed 800 mg/24h, to prevent fetal bradycardia 1
Postpartum considerations: Neonates should be monitored for potential side effects of labetalol, including hypotension, hypoglycemia, and bradycardia 1
Transition planning: Women with hypertension who become pregnant should be transitioned to methyldopa, nifedipine, and/or labetalol during pregnancy 3
By following these evidence-based recommendations, clinicians can effectively manage pregnancy-induced hypertension while minimizing risks to both mother and fetus.