What are the management guidelines for hypertension in pregnancy?

Management of Hypertension in Pregnancy: Philippine Clinical Practice Guidelines

Classification and Diagnosis

Hypertension in pregnancy should be classified based on timing of onset and presence of proteinuria, with blood pressure ≥140/90 mmHg defining hypertension. 1

The classification system includes:

• Chronic hypertension: Present before pregnancy or diagnosed before 20 weeks gestation 1, 2
• Gestational hypertension: New-onset hypertension after 20 weeks without proteinuria 1, 2
• Preeclampsia: Gestational hypertension with proteinuria (≥0.3 g/24h or albumin-to-creatinine ratio ≥30 mg/mmol) or evidence of maternal organ dysfunction 1, 2
• Superimposed preeclampsia: Chronic hypertension with worsening BP and proteinuria ≥3 g/day after 20 weeks 1, 2

Treatment Thresholds

Initiate antihypertensive treatment at BP ≥140/90 mmHg in women with gestational hypertension, preeclampsia, chronic hypertension with superimposed gestational hypertension, or hypertension with subclinical organ damage. 1, 2

For all other pregnant women with hypertension, treatment threshold is BP ≥150/95 mmHg. 1, 2, 3

BP ≥170/110 mmHg constitutes a hypertensive emergency requiring immediate hospitalization and treatment. 1, 2

Target Blood Pressure

Target BP should be below 140/90 mmHg, but diastolic BP should not fall below 80 mmHg to ensure adequate uteroplacental perfusion. 2

Avoid excessive BP reduction as this may compromise fetal blood flow. 4

First-Line Pharmacological Management

For non-severe hypertension, use methyldopa, labetalol, or extended-release nifedipine as first-line agents. 1, 2, 5

• Methyldopa: Has the longest safety record with adequate infant follow-up (7.5 years) and is considered the drug of choice 1, 2, 3
• Labetalol: Comparable efficacy to methyldopa and can be given orally or intravenously 1, 2, 3, 6
• Nifedipine: Extended-release formulation preferred; effective and safe throughout pregnancy 1, 2, 5

Management of Hypertensive Emergencies

For severe hypertension (BP ≥170/110 mmHg), immediately administer IV labetalol, oral methyldopa, or oral nifedipine. 1, 2

The goal is to decrease mean BP by 15-25% with target SBP 140-150 mmHg and DBP 90-100 mmHg. 4

• IV labetalol has now supplanted hydralazine as the preferred parenteral agent 6
• IV hydralazine is no longer first-line due to more perinatal adverse effects 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 (5-100 mg/min IV) is the drug of choice for preeclampsia with pulmonary edema 1

Contraindicated Medications

ACE inhibitors, ARBs, and direct renin inhibitors are strictly contraindicated throughout pregnancy due to severe fetotoxicity. 2, 3, 6

Atenolol should be avoided due to association with fetal growth restriction, particularly with prolonged use. 1, 3, 6

Non-Pharmacological Management

For mild hypertension (SBP 140-150 mmHg or DBP 90-99 mmHg), non-pharmacological measures include:

• Normal diet without salt restriction, particularly near delivery, as salt restriction may induce low intravascular volume 1, 2
• Limitation of activities and bed rest in left lateral position 1, 2, 4
• Avoid weight reduction during pregnancy in obese women, as it may reduce neonatal weight 1
• Recommended weight gain: <6.8 kg for obese women (BMI ≥30), 6.8-11.2 kg for overweight women (BMI 25-29.9), and 11.2-15.9 kg for normal BMI 1

Prevention Strategies

Low-dose aspirin (75-100 mg/day) should be administered at bedtime starting before 16 weeks gestation in women with history of early-onset preeclampsia (<28 weeks). 1, 2

Calcium supplementation of at least 1 g daily during pregnancy reduces preeclampsia risk, particularly in high-risk women. 1

Fish oil, vitamin supplements, and other nutrient supplementation have no proven role in prevention. 1

Monitoring Requirements

All pregnant women with hypertension require periodic assessment for proteinuria in the second half of pregnancy to screen for preeclampsia. 1

• If dipstick is ≥1+, promptly evaluate with ACR in spot urine or 24-hour collection 1
• ACR <30 mg/mmol reliably rules out proteinuria 1
• Monitor for warning signs: persistent headache, visual disturbances, epigastric pain, coagulation abnormalities 1, 2, 4
• sFlt/PlGF ratio ≤38 can exclude preeclampsia development in the next week when clinically suspected 1

Delivery Indications

Induction of delivery is indicated in gestational hypertension with proteinuria when adverse conditions develop, including visual disturbances, coagulation abnormalities, or fetal distress. 1, 2

Delivery is recommended for preeclampsia at term. 1

Postpartum Management

Continue antihypertensive medications postpartum with gradual tapering rather than abrupt cessation. 1, 2

• Safe medications for breastfeeding: labetalol, nifedipine, methyldopa, enalapril, and beta-blockers 2
• Avoid NSAIDs for postpartum analgesia in women with preeclampsia unless other analgesics fail, especially with renal disease, placental abruption, or AKI 1
• Avoid diuretics as they may reduce milk production 2

All women must be reviewed at 3 months postpartum to ensure BP, urinalysis, and laboratory abnormalities have normalized. 1, 2

If proteinuria or hypertension persists, initiate appropriate referral for further investigation. 1

Long-Term Cardiovascular Risk

Women with hypertensive disorders of pregnancy face significant long-term cardiovascular risks and require annual medical review lifelong. 1, 2, 5

Recommendations include:

• Aim to achieve prepregnancy weight by 12 months and limit interpregnancy weight gain 1, 2
• Adopt healthy lifestyle including regular exercise, healthy diet, and ideal body weight maintenance 1, 2
• Obstetric history should become part of cardiovascular risk assessment 5

Critical Pitfalls to Avoid

• Never stop antihypertensive medications abruptly postpartum, as eclamptic seizures may develop for the first time in early postpartum period 1
• Do not reduce diastolic BP below 80 mmHg, as this compromises uteroplacental perfusion 2, 4
• Confirm severe hypertension readings within 15 minutes before initiating emergency treatment 4
• Do not use ergot derivatives for postpartum hemorrhage in hypertensive women, as they can worsen BP 1