What is the recommended management of hypertension in pregnancy?

Management of Hypertension in Pregnancy

For pregnant women with gestational hypertension, pre-existing hypertension with superimposed gestational hypertension, or hypertension with subclinical organ damage, initiate antihypertensive treatment at BP ≥140/90 mmHg; for all other pregnant women with chronic hypertension, treatment should begin at BP ≥150/95 mmHg. 1, 2, 3

Blood Pressure Thresholds for Treatment

The treatment threshold depends on the specific hypertensive disorder:

• Lower threshold (≥140/90 mmHg): Start treatment at this level for women with gestational hypertension (with or without proteinuria), pre-existing hypertension with superimposed gestational hypertension, or hypertension with subclinical organ damage or symptoms at any time during pregnancy 1, 2, 3

• Higher threshold (≥150/95 mmHg): For all other pregnant women with chronic hypertension without the above features, treatment begins at this higher threshold 1, 3

• Target BP during treatment: Aim for diastolic BP of 85 mmHg and systolic BP between 110-140 mmHg to ensure adequate uteroplacental perfusion while protecting the mother 2, 3

First-Line Pharmacological Agents

Methyldopa, labetalol, and long-acting nifedipine are the three preferred first-line agents for chronic blood pressure control during pregnancy. 2, 3

Methyldopa

• Remains the drug of choice based on the longest safety data, including 7.5-year follow-up studies showing no adverse effects on child development 1, 4
• Important caveat: Should be avoided postpartum due to risk of postnatal depression 3
• May interfere with laboratory tests for pheochromocytoma (falsely elevated urinary catecholamines) 4

Labetalol

• Has efficacy comparable to methyldopa and can be given orally or intravenously 1, 5
• Critical warning: Should not be used concomitantly with calcium channel blockers due to risk of severe hypotension 3, 5
• Small amounts (0.004% of maternal dose) are excreted in breast milk 5

Nifedipine (long-acting)

• A 2019 randomized controlled trial of 894 women demonstrated that nifedipine retard achieved blood pressure control within 6 hours in 84% of women, significantly more than methyldopa (76%, p=0.03) 6
• Particularly useful for acute management of severe hypertension when given as immediate-release formulation 3

Management of Severe Hypertension (Emergency)

BP ≥170/110 mmHg constitutes a hypertensive emergency requiring immediate hospitalization and treatment within 15 minutes to prevent maternal stroke. 1, 3

First-line agents for acute severe hypertension:

• Oral immediate-release nifedipine: Preferred first-line option 3
• Intravenous labetalol: Equally effective alternative 1, 3
• Oral methyldopa: Can be used but has slower onset 1

Important changes in practice:

• Intravenous hydralazine is no longer the drug of choice as it is associated with more perinatal adverse effects than other drugs 1
• Sodium nitroprusside (0.25-5.0 mg/kg/min IV) is reserved for hypertensive crises, but prolonged use risks fetal cyanide poisoning 1
• Nitroglycerin (glyceryl trinitrate) IV infusion is the drug of choice specifically for pre-eclampsia associated with pulmonary edema 1

Non-Pharmacological Management

For pregnant women with SBP 140-150 mmHg or DBP 90-99 mmHg, non-pharmacological management is recommended initially 1:

• Close supervision with limitation of activities and some bed rest in left lateral position 1
• Normal diet without salt restriction is advised, particularly close to delivery, as salt restriction may induce low intravascular volume 1
• Low-dose aspirin (75-100 mg/day) should be used prophylactically in women with history of early-onset (<28 weeks) pre-eclampsia, administered at bedtime starting before 16 weeks gestation and continued until delivery 1
• Calcium supplementation of at least 1 g daily almost halved the risk of pre-eclampsia, with greatest effect in high-risk women, though evidence is conflicting 1
• Weight reduction is not recommended during pregnancy in obese women as it can lead to reduced neonatal weight 1

Timing of Delivery

• Gestational hypertension with proteinuria and adverse conditions (visual disturbances, coagulation abnormalities, fetal distress): Induction of delivery is indicated 1, 2
• Pre-eclampsia at term (37 weeks): Recommend delivery 2, 3
• Gestational hypertension without preeclampsia: Delivery can be delayed until 39+6 weeks if BP remains controlled 3

Contraindicated Medications

ACE inhibitors, angiotensin receptor blockers (ARBs), and direct renin inhibitors are strictly contraindicated in pregnancy due to severe fetotoxicity, particularly in the second and third trimesters 1, 7, 8

• If taken inadvertently during first trimester, switch to another medication immediately and perform close monitoring including fetal ultrasound 1
• Atenolol should also be avoided due to concerns with fetal growth 8

Postpartum Management

• Switch from methyldopa to an alternative agent due to postnatal depression risk 3
• BP typically rises over the first 5 postpartum days; women may become hypertensive again after initial normalization 3
• Annual medical review lifelong is recommended for cardiovascular risk assessment, as women with gestational hypertension or preeclampsia have significantly increased lifetime cardiovascular risk 2, 3