Management of Hypertension in Pregnancy

Classification

Blood Pressure Thresholds and Treatment Targets

When to Treat (2024 ESC Guidelines)

• Gestational HTN, pre-existing HTN with organ damage, or HTN with symptoms: Start antihypertensives at SBP ≥140 or DBP ≥90 mmHg (Class I, Level B)
• All other cases: Initiate treatment at SBP ≥150 or DBP ≥95 mmHg (Class I, Level C)
• Severe HTN (>160/110 mmHg): Treat urgently; sustained severe HTN for >15 minutes is a hypertensive emergency

BP Targets

• ACOG recommends maintaining BP between 120-160 mmHg systolic and 80-105 mmHg diastolic
• A conservative approach is appropriate for mild-to-moderate HTN (SBP 140-159 / DBP 90-109), as aggressive lowering risks impairing uteroplacental perfusion

Antihypertensive Medications

First-Line Oral Agents

Acute/Severe Hypertension (IV Agents)

• Labetalol IV: 20 mg, escalate to 40 mg at 10 minutes if inadequate response
• Hydralazine IV/IM: 5-10 mg, repeat every 20 minutes - used widely but carries increased risk of maternal hypotension and placental abruption vs labetalol
• Nicardipine IV: Extensive safety data from use as tocolytic; effective for BP control

Second-Line Agents

• Metoprolol (long-acting available), verapamil, diltiazem - limited data but no known fetal harm
• Hydralazine (oral) - extensive experience but more side effects

Agents to Avoid or That Are Contraindicated

Preeclampsia Management

Diagnostic Criteria

• Proteinuria ≥300 mg/24h (or PCR ≥0.3)
• Thrombocytopenia (<100,000/µL)
• Renal insufficiency (creatinine >1.1 mg/dL)
• Impaired liver function (transaminases ≥2x ULN)
• Pulmonary oedema
• New-onset headache unresponsive to analgesia or visual symptoms

Severe Features

• BP ≥160/110 mmHg on two occasions ≥4 hours apart
• Severe headache, visual disturbance, altered mental status
• Pulmonary oedema
• Thrombocytopenia <100,000, transaminases ≥2x ULN
• Serum creatinine >1.1 mg/dL
• IUGR/abnormal uteroplacental Dopplers

Definitive Treatment

• ≥37 weeks with any preeclampsia: deliver
• ≥34 weeks with severe preeclampsia: deliver
• <34 weeks with severe preeclampsia: consider expectant management in tertiary centre with fetal and maternal monitoring; corticosteroids for lung maturity; deliver if maternal or fetal status deteriorates
• AKI in setting of preeclampsia: urgent delivery indicated

Seizure Prophylaxis (Eclampsia Prevention)

• Indicated in severe preeclampsia or with CNS manifestations (headache, visual disturbance, altered sensorium)
• Continue for at least 24-48 hours postpartum
• ~20% of eclamptic seizures occur >48 hours after delivery, so postpartum vigilance is essential
• Dosing: loading dose 4-6 g IV over 15-20 minutes, then 1-2 g/hour maintenance

Prevention of Preeclampsia

• Low-dose aspirin (75-150 mg/day): Recommended from 12-16 weeks gestation in women at high risk (prior preeclampsia, chronic HTN, multifetal gestation, renal disease, diabetes, autoimmune disease). Reduces risk by ~10-15%.
• Calcium supplementation (1.5-2 g/day): Recommended in populations with low dietary calcium intake
• Screening with first-trimester biomarkers: Mean arterial pressure, uterine artery Pulsatility Index, PlGF, PAPP-A (combined test) identifies >75% of early-onset preeclampsia at 5-10% false positive rate

Chronic Hypertension in Pregnancy - Special Considerations

• Pre-conception counselling: Switch to pregnancy-safe agents before conception (stop ACEi/ARB); assess for secondary HTN causes (primary aldosteronism, renal artery stenosis, phaeochromocytoma, OSA)
• First trimester BP fall: BP physiologically decreases to a nadir around 20-30 weeks; antihypertensive doses may need reduction to avoid hypotension
• Monitor for superimposed preeclampsia throughout pregnancy
• Secondary causes: Present in ≥10% of chronic HTN in pregnancy; phaeochromocytoma can be life-threatening if unrecognized at labour

Postpartum Management

• HTN can persist or worsen postpartum; ~20% of eclamptic seizures occur >48 hours post-delivery
• Continue antihypertensives postpartum as needed; most oral agents are compatible with breastfeeding (methyldopa, labetalol, nifedipine)
• ACEi (enalapril) is compatible with breastfeeding and can be introduced postpartum
• Women with gestational HTN/preeclampsia are at increased long-term risk for hypertension and cardiovascular disease - flag for follow-up at 6-8 weeks and ongoing cardiovascular risk monitoring

HELLP Syndrome

• Diagnosis: microangiopathic haemolysis, AST/ALT ≥2x ULN, platelets <100,000/µL
• Treatment: delivery (irrespective of gestational age in most cases), magnesium sulfate, platelet transfusion if <50,000/µL and delivering, corticosteroids may be given for fetal lung maturity
• AKI incidence 10-25% in severe HELLP

Key Guideline Sources

• 2024 ESC Guidelines for the Management of Elevated Blood Pressure (Section 9.2) - updated treatment thresholds and recommendations
• ACOG Practice Bulletin 222 - Gestational Hypertension and Preeclampsia (ongoing updates)
• ISSHP 2021/2022 Classification, Diagnosis & Management Recommendations (Magee et al., Pregnancy Hypertens 2022;27:148-169)
• CHIPS Trial - NEJM 2015;372:407-417 - foundational evidence for tight BP control targets

Recent Evidence Note: A 2024 comprehensive review (PMID: 39494413) highlights persistent healthcare disparities in hypertensive disorders of pregnancy outcomes and ongoing refinement of biomarker-based risk stratification. The 2024 ESC Guidelines represent the most current major guideline update, lowering the treatment threshold for gestational HTN to ≥140/90 mmHg (previously 150/95 in many frameworks).