Latest guidelines for management of hypertension in pregnancy
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Management of Hypertension in Pregnancy
Classification
Hypertensive disorders of pregnancy fall into four categories (ACOG):
| Category | Definition |
|---|---|
| Chronic hypertension | Pre-existing or diagnosed before 20 weeks gestation |
| Gestational hypertension | New-onset BP ≥140/90 mmHg after 20 weeks, no proteinuria |
| Preeclampsia | Gestational hypertension + proteinuria (or end-organ damage) |
| Superimposed preeclampsia | Preeclampsia developing in a woman with chronic hypertension |
ACOG further stratifies chronic hypertension as:
- Mild to moderate: SBP 140–159 or DBP 90–109 mmHg
- Severe: SBP ≥160 or DBP ≥110 mmHg
Note: AHA/ACC define hypertension at a lower threshold (Stage 1: ≥130/80 mmHg), so some women enter pregnancy already on treatment that doesn't meet ACOG's pregnancy threshold. — Creasy & Resnik's Maternal-Fetal Medicine
When to Treat (BP Thresholds)
- Severe hypertension (SBP ≥160 or DBP ≥105–110 mmHg): antihypertensive therapy is clearly indicated to prevent stroke and cardiovascular complications.
- Mild-to-moderate hypertension (BP <160/105 mmHg): evidence is limited. Multiple meta-analyses show treatment reduces progression to severe hypertension but has no benefit on preeclampsia, neonatal death, preterm birth, or SGA.
- ACOG recommends against routine antihypertensive use for BP <160/105 mmHg in the absence of end-organ damage.
- Aggressive treatment of mild-to-moderate hypertension may impair fetal growth by reducing uteroplacental perfusion.
Brenner and Rector's The Kidney
CHIPS Trial (Control of Hypertension In Pregnancy Study): Tight control (target DBP 85 mmHg) vs less-tight control (DBP 100 mmHg):
- No difference in pregnancy loss or need for high-level neonatal care
- Tight control significantly reduced severe hypertension (27.5% vs 40.6%), thrombocytopenia, and transaminitis
- Current guidance: target DBP 85 mmHg is safe and reduces maternal complications
Antihypertensive Drug Choice
First-Line Agents in Pregnancy
| Drug | Route | Notes |
|---|---|---|
| Labetalol | IV (acute) / oral | First-line for chronic and acute hypertension |
| Methyldopa | Oral | Long safety record; preferred for chronic use |
| Nifedipine (CCB) | Oral / sublingual (avoid) | Effective; avoid concurrent MgSO₄ (risk of neuromuscular block) |
| Hydralazine | IV | Used for acute severe hypertension |
Drugs to AVOID in Pregnancy
| Drug | Reason |
|---|---|
| ACE inhibitors (e.g., enalapril, ramipril) | Fetal renal dysgenesis, oligohydramnios, neonatal renal failure |
| ARBs (e.g., losartan) | Same fetal toxicity as ACEi |
| Direct renin inhibitors (aliskiren) | Same mechanism, contraindicated |
| Spironolactone | Theoretical risk of inadequate virilization of male fetuses (antiandrogenic) |
| Atenolol | Associated with fetal growth restriction |
Eplerenone appears a safer alternative to spironolactone when conventional agents are inadequate (e.g., primary hyperaldosteronism in pregnancy).
Management of Acute Severe Hypertension
Acute severe hypertension (SBP ≥160 or DBP ≥105–110 mmHg) requires urgent treatment within 30–60 minutes to prevent maternal stroke.
IV/acute agents:
- Labetalol IV: 20 mg bolus, repeat every 10 min (max 300 mg)
- Hydralazine IV: 5–10 mg bolus every 20 min
- Nifedipine oral: 10–20 mg, repeat in 30 min if needed
Preeclampsia: Key Additional Interventions
- Definitive treatment: delivery (timing depends on gestational age and severity)
- Magnesium sulfate: seizure prophylaxis for severe features; also neuroprotection for the neonate if <32 weeks
- Do not use MgSO₄ and nifedipine together without monitoring (risk of profound hypotension and neuromuscular blockade)
- Threshold for delivery: ≥37 weeks for preeclampsia without severe features; ≥34 weeks with severe features
Chronic Hypertension: Preconception and Monitoring
- Preconception: optimize BP with pregnancy-safe agents; stop ACEi/ARBs before conception or as soon as pregnancy confirmed
- Baseline workup at first visit: urinalysis, creatinine, LFTs, CBC, uric acid — establishes reference for later detecting superimposed preeclampsia
- Fetal monitoring: serial growth ultrasounds (risk of FGR); antenatal fetal surveillance from 32–36 weeks
- Risk counseling: preeclampsia occurs in ~25% of chronically hypertensive women vs 4% in normotensives; 3–10× increased risk of preterm birth, SGA, perinatal death, maternal stroke, and renal failure
Secondary Hypertension in Pregnancy
At least 10% of chronic hypertension in pregnancy has a secondary cause. Consider workup for:
- Renal artery stenosis (fibromuscular dysplasia) — suspect if severe/resistant; diagnose with MRA
- Pheochromocytoma — rare but can be fatal at delivery; must be diagnosed antenatally
- Primary hyperaldosteronism — may worsen in pregnancy; eplerenone preferred over spironolactone
- Obstructive sleep apnea — 40% of hypertensive pregnant women in one study; screen in obese/snorers
Sources:
- Brenner and Rector's The Kidney, 2-Volume Set
- Creasy & Resnik's Maternal-Fetal Medicine: Principles and Practice
- National Kidney Foundation Primer on Kidney Diseases, 8e
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