What are the recommended medications for managing hypertension (Htn) in pregnancy?

Hypertension Management in Pregnancy

For chronic hypertension in pregnancy, use oral labetalol, extended-release nifedipine, or methyldopa as first-line agents, with labetalol and nifedipine preferred over methyldopa due to superior side effect profiles and efficacy in preventing preeclampsia. 1, 2

First-Line Medication Selection

Preferred Agents

• Extended-release nifedipine and labetalol are the preferred first-line agents for chronic hypertension during pregnancy, offering better tolerability and adherence compared to methyldopa 1, 2
• Nifedipine provides once-daily dosing which improves patient adherence, and has established safety data throughout pregnancy 1
• Labetalol and nifedipine appear superior to methyldopa in preventing preeclampsia 1
• A randomized trial of 894 women demonstrated that nifedipine achieved blood pressure control (120-150/70-100 mmHg) within 6 hours in 84% of patients versus 77% with labetalol and 76% with methyldopa 3

Methyldopa Considerations

• Methyldopa has the longest safety record in pregnancy but should be considered second-line due to its side effect profile 1, 4
• Methyldopa must be avoided postpartum due to significant risk of postpartum depression 5, 1
• Despite its historical use, methyldopa is less effective than labetalol or nifedipine for preventing preeclampsia 1

Treatment Thresholds and Targets

When to Initiate Treatment

• Start antihypertensive therapy at BP ≥140/90 mmHg in women with gestational hypertension (with or without proteinuria), pre-existing hypertension with superimposed gestational hypertension, or hypertension with subclinical organ damage 5, 6
• For uncomplicated pre-existing hypertension without these features, treatment threshold is BP ≥150/95 mmHg 5

Blood Pressure Goals

• Target diastolic BP of 85 mmHg and systolic BP between 110-140 mmHg to prevent severe maternal complications while maintaining adequate uteroplacental perfusion 5, 6, 2
• Reduce or cease antihypertensive drugs if diastolic BP falls below 80 mmHg to avoid compromising uteroplacental perfusion 1

Management of Severe Hypertension (≥170/110 mmHg)

Emergency Protocol

• BP ≥170/110 mmHg constitutes a hypertensive emergency requiring hospitalization and treatment within 60 minutes 5, 1
• Continue antihypertensive treatment during labor and delivery to maintain BP <160/110 mmHg 5

Acute Severe Hypertension Medications

• First-line options: IV labetalol, oral extended-release nifedipine, or oral methyldopa 5, 2
• IV hydralazine is no longer the drug of choice due to association with more perinatal adverse effects compared to other agents 5
• For hypertensive crisis: sodium nitroprusside IV at 0.25-5.0 mg/kg/min, though prolonged use risks fetal cyanide poisoning 5
• For pre-eclampsia with pulmonary edema: IV nitroglycerin 5 mg/min, titrated every 3-5 minutes to maximum 100 mg/min 5

Critical Safety Considerations

Contraindicated Medications

• ACE inhibitors, ARBs, direct renin inhibitors, and mineralocorticoid receptor antagonists are absolutely contraindicated throughout pregnancy due to fetotoxicity, renal dysgenesis, and oligohydramnios 5, 1, 2
• These agents must be discontinued before conception in women planning pregnancy 1

Important Drug Interactions and Precautions

• Never use nifedipine concurrently with magnesium sulfate due to risk of precipitous hypotension, myocardial depression, and potential fetal compromise 5, 1
• Use only long-acting nifedipine formulations for maintenance therapy; immediate-release nifedipine is reserved exclusively for acute severe hypertension 1
• Avoid sublingual or IV nifedipine due to risk of uncontrolled hypotension and maternal myocardial infarction 1
• Labetalol may cause neonatal bradycardia and increase risk of small-for-gestational-age infants 1, 7

Postpartum Management

Medication Adjustments

• Switch methyldopa to an alternative agent immediately postpartum due to depression risk 5, 1
• Nifedipine, labetalol, metoprolol, and enalapril are safe for breastfeeding mothers 5, 1
• Avoid enalapril if neonate is premature or has renal failure 1
• Diuretics may reduce milk production and are generally not preferred in breastfeeding women 1

Monitoring Protocol

• BP typically rises postpartum over the first 5 days; women may become hypertensive again in the first postnatal week even if normotensive immediately after delivery 5
• Check BP and urine at 6 weeks postpartum; confirm persistent hypertension with 24-hour ambulatory monitoring 5
• Women under age 40 with persistent hypertension should be assessed for secondary causes 5

Long-Term Cardiovascular Risk

• Women with gestational hypertension or pre-eclampsia have 4-fold increased risk of developing chronic hypertension and more than 2-fold increased risk of ischemic heart disease in later life 5
• Annual cardiovascular risk assessment is recommended lifelong for all women with pregnancy-related hypertensive disorders 1, 6
• Emphasize lifestyle modifications including exercise, proper nutrition, and maintaining ideal body weight 2