Latest guidelines for management of hypertension in pregnancy
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Management of Hypertension in Pregnancy
Classification
Hypertensive disorders affect up to 10% of pregnancies. Key categories:
| Category | Definition |
|---|---|
| Chronic hypertension | Pre-existing or onset before 20 weeks |
| Gestational hypertension | New-onset ≥20 weeks, no proteinuria; 6–17% of nulliparas, 2–4% of paras |
| Preeclampsia | BP ≥140/90 mmHg + proteinuria ≥300 mg/24h (or PCR ≥0.3), onset ≥20 weeks |
| Superimposed preeclampsia | Preeclampsia developing on chronic hypertension |
| Eclampsia | Seizures in the preeclampsia setting; now ~1 in 2000–3000 deliveries |
Diagnostic Criteria for Preeclampsia
- BP ≥ 140/90 mmHg on two occasions
- Proteinuria ≥ 300 mg/24h or urine protein:creatinine ratio ≥ 0.3
- Once proteinuria is established and the diagnosis confirmed, repeat quantification is not necessary
Severe features include:
- SBP ≥ 160 or DBP ≥ 110 mmHg
- Thrombocytopenia (platelets < 100,000/µL)
- Renal insufficiency (creatinine > 1.1 mg/dL)
- Impaired liver function (elevated transaminases ×2 normal)
- Pulmonary edema
- New-onset headache or visual disturbances
HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low Platelets) represents a severe variant.
Goals of Antihypertensive Therapy
- Severe hypertension (SBP ≥160 or DBP ≥105 mmHg): Treat immediately to prevent maternal stroke and cardiovascular complications
- Mild-to-moderate hypertension: Evidence for treatment is less definitive; treatment reduces risk of severe hypertension but does not clearly prevent preeclampsia or IUGR
- Target BP: generally 130–155/80–105 mmHg — avoid aggressive lowering that compromises uteroplacental perfusion
Antihypertensive Drug Choice
First-Line Oral Agents
| Drug | Notes |
|---|---|
| Methyldopa 250 mg BD | Centrally acting α2-agonist; most extensive safety data; preferred first-line. Drawbacks: short half-life, sedation, rare hepatotoxicity or hemolytic anemia |
| Labetalol 100 mg BD | α1 + non-selective β-blocker; preferred β-blocker due to α-blockade preserving uteroplacental blood flow; can exacerbate reactive airways disease |
| Long-acting nifedipine 30 mg OD | Calcium channel blocker; once-daily dosing; may cause edema |
Second-Line Oral Agents
| Drug | Notes |
|---|---|
| Metoprolol | Long-acting formulation possible; less safety data than labetalol |
| Verapamil, diltiazem | Limited data but no known fetal adverse effects |
| Clonidine | Comparable to methyldopa in mechanism; fewer data |
Drugs to Generally Avoid
| Drug | Reason |
|---|---|
| Atenolol | Associated with fetal growth restriction |
| Diuretics | May impair pregnancy-associated plasma volume expansion |
| Nitroprusside | Risk of fetal cyanide poisoning if used > 4 hours |
Contraindicated
| Drug | Reason |
|---|---|
| ACE inhibitors | Multiple fetal anomalies (renal tubular dysgenesis, oligohydramnios, hypocalvaria) |
| Angiotensin receptor blockers (ARBs) | Similar risks as ACE inhibitors |
Management of Severe Acute Hypertension (≥160/110 mmHg)
This constitutes a hypertensive emergency requiring urgent treatment within minutes to hours.
Oral
| Drug | Dose |
|---|---|
| Nifedipine IR | 10–20 mg, repeat at 20 min; then 10–20 mg q2–6h; max 180 mg/day |
Intravenous (Preferred Route for Acute Control)
| Drug | Dose |
|---|---|
| Labetalol (preferred) | 10–20 mg IV, then 1–2 mg/min infusion OR 20–80 mg bolus q10–30 min; max 300 mg |
| Hydralazine | 5 mg IV initially, then 0.5–10 mg/hr OR 5–10 mg q20–40 min; max 20 mg. Note: higher risk of maternal hypotension and placental abruption |
| Nicardipine | IV infusion; extensive safety data from tocolytic use |
Seizure Prophylaxis and Treatment (Eclampsia)
- Magnesium sulfate is the drug of choice for seizure prevention in severe preeclampsia and treatment of eclampsia
- Indicated for CNS manifestations: new headache, visual disturbance, altered mental status
- Also indicated for postpartum women with CNS manifestations — ~20% of eclampsia episodes occur > 48 hours after delivery
Definitive Treatment
- Delivery is the only cure for preeclampsia/eclampsia
- If severe preeclampsia develops with end-organ damage and the fetus is mature → deliver
- If the fetus is very preterm → hospitalization + pharmacotherapy to allow further fetal maturation, alongside corticosteroids for lung maturity and antibiotics if indicated
Chronic Hypertension in Pregnancy: Special Points
- Screen for secondary causes (renal artery stenosis, primary hyperaldosteronism, OSA, pheochromocytoma) — present in at least 10% of women with chronic hypertension in pregnancy
- Stop ACE inhibitors/ARBs as soon as pregnancy is confirmed
- Spironolactone: theoretical risk of inadequate virilization of male fetuses; eplerenone preferred if mineralocorticoid antagonism is needed
- OSA: ~40% of women with hypertension in pregnancy show OSA evidence on polysomnography; screen high-risk women (snoring, obesity)
- Monitor closely for superimposed preeclampsia throughout pregnancy
Postpartum Considerations
- Hypertension may worsen or newly develop in the first days after delivery
- Continue antihypertensive therapy postpartum as needed
- Eclampsia can occur up to 48+ hours postdelivery; maintain vigilance for CNS symptoms
Sources: Brenner and Rector's The Kidney, 2-Volume Set | Goldman-Cecil Medicine | Goodman & Gilman's The Pharmacological Basis of Therapeutics
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