Management of Hypertension in Pregnancy - Current Guidelines

1. Classification

2. When to Start Antihypertensive Therapy - The CHAP Trial Paradigm Shift

• Mild-to-moderate hypertension: Target diastolic BP ~85 mmHg (supported by the CHIPS trial, which showed equivalent fetal outcomes with tight vs. less-tight control at DBP 85 vs. 100 mmHg, with fewer maternal complications in the tight-control group)
• Severe hypertension (≥160/110 mmHg): Treat urgently within 30-60 minutes to reduce stroke risk

3. Antihypertensive Drug Selection

First-Line Oral Agents

Intravenous Agents (acute/inpatient)

Second-Line Oral Agents

• Hydralazine (oral): Widely used but tachycardia is common; max 300 mg/day
• Metoprolol: Acceptable alternative to labetalol; less safety data
• Verapamil / Diltiazem: No evidence of fetal harm; limited data

Drugs to Avoid or Use with Caution

• Brenner and Rector's The Kidney, Table 48.6; NKF Primer on Kidney Diseases, Table 47.1

4. Preeclampsia

Diagnosis

• BP ≥140/90 mmHg after 20 weeks + proteinuria >300 mg/24h (or PCR ≥0.3)
• OR hypertension with any end-organ damage (thrombocytopenia, renal insufficiency, impaired liver function, pulmonary edema, visual/neurological symptoms) even without proteinuria

Severe Features of Preeclampsia

• BP ≥160/110 mmHg on two occasions
• Thrombocytopenia (<100,000/µL)
• Renal insufficiency (creatinine >1.1 mg/dL or doubling)
• Impaired liver function (AST/ALT >2x upper limit) with RUQ/epigastric pain
• Pulmonary edema
• New-onset headache unresponsive to analgesia, visual disturbances

HELLP Syndrome

Definitive Treatment: Delivery

• The only cure for preeclampsia is delivery of the placenta
• At ≥37 weeks or with severe features at any gestational age: delivery is recommended
• If <34 weeks with severe features: individualize timing; hospitalize and consider steroids for fetal lung maturity; magnesium sulfate for neuroprotection
• If <37 weeks without severe features: expectant management with close monitoring is reasonable

5. Acute Severe Hypertension Management

1. Confirm BP on repeat measurement within 15 minutes
2. Initiate IV access and fetal monitoring
3. Administer antihypertensive therapy:
   • Labetalol 20 mg IV → 40 mg at 10 min → 80 mg at 10 min (max 300 mg total)
   • OR Hydralazine 5-10 mg IV q20 min
   • OR Oral nifedipine 10 mg capsule (not sustained release) for rapid-onset effect
4. Target: Reduce BP to <160/110 mmHg acutely, then stabilize at 140-150/90-100 mmHg
5. Magnesium sulfate (4 g IV loading dose, 1-2 g/hr maintenance) for seizure prophylaxis/eclampsia prevention - not an antihypertensive

6. Seizure Prevention - Magnesium Sulfate

• Magnesium sulfate is the drug of choice for seizure prophylaxis in severe preeclampsia and for treatment/prevention of eclampsia
• Standard regimen: 4-6 g IV loading dose over 15-20 minutes, followed by 1-2 g/hr infusion
• Continue for 24-48 hours postpartum
• Approximately 20% of eclamptic seizures occur more than 48 hours after delivery - postpartum vigilance is essential
• Monitor for magnesium toxicity: loss of patellar reflexes (first sign), respiratory depression, cardiac arrest. Antidote: calcium gluconate 1 g IV

7. Prevention of Preeclampsia

• Recommended for women at high risk of preeclampsia
• Dose: 81-162 mg/day (most guidelines use 150 mg in Europe, 81 mg in US)
• Started at 12-16 weeks (ideally before 16 weeks)
• Reduces risk of preterm preeclampsia by ~62% (Lancet ASPRE trial)
• High-risk criteria (one major or multiple moderate risk factors): prior preeclampsia, multifetal gestation, chronic hypertension, diabetes, CKD, autoimmune conditions (SLE, antiphospholipid syndrome)

• WHO recommends 1.5-2 g/day for women with low dietary calcium intake
• Evidence for reducing preeclampsia risk, particularly in low-income populations

8. Postpartum Management

• BP often worsens in the first 48-72 hours postpartum as fluid shifts occur
• Continue antihypertensives postpartum; many women with chronic hypertension will need ongoing therapy
• NSAIDs (ibuprofen) commonly given for postpartum pain should be used with caution in hypertensive women as they can raise BP
• Postpartum hypertension that is new-onset and unresolved by 12 weeks defines chronic hypertension
• Women with a history of preeclampsia are at significantly elevated long-term cardiovascular risk and should receive cardiovascular counseling

9. Key Guideline Summary Table

• Brenner and Rector's The Kidney, 2-Volume Set - Ch. 48 (Management of Hypertension in Pregnancy, Drug Safety Table 48.6)
• NKF Primer on Kidney Diseases, 8e - Table 47.1 (Oral Antihypertensive Medications in Pregnancy)
• Goodman & Gilman's Pharmacological Basis of Therapeutics - Ch. 14 (Pregnancy-Induced Hypertension)
• CHAP Trial review [PMID 36912258] - Holliman et al., Curr Opin Obstet Gynecol 2023
• ESC 2024 Guidelines for management of elevated blood pressure (Section 9.2)
• ACOG/SMFM practice advisory 2022 (post-CHAP)

Clinical note: Management of HDP is evolving rapidly. The CHAP trial fundamentally changed the threshold for treating mild chronic hypertension from ≥160/105 to ≥140/90 mmHg. Always verify current local/national guidelines, as ACOG and ISSHP recommendations may be updated. Institutional protocols may also vary for acute severe hypertension.