What is the management approach for Pregnancy-Induced Hypertension (PIH)?

Management of Pregnancy-Induced Hypertension (PIH)

The management of Pregnancy-Induced Hypertension (PIH) requires prompt treatment of severe hypertension (BP ≥160/110 mmHg), with antihypertensive therapy recommended for any persistent non-severe hypertension to prevent progression to severe hypertension and associated complications. 1

Classification and Diagnosis

PIH can be classified into four categories:

• Pre-existing hypertension: BP ≥140/90 mmHg that predates pregnancy or develops before 20 weeks of gestation
• Gestational hypertension: Pregnancy-induced hypertension without proteinuria, developing after 20 weeks
• Preeclampsia: Gestational hypertension with significant proteinuria (>300 mg/L or >500 mg/24h)
• Pre-existing hypertension with superimposed gestational hypertension with proteinuria 1, 2

Diagnosis should be based on at least two high blood pressure readings on separate occasions. 24-hour ambulatory blood pressure monitoring is superior to conventional measurements for predicting complications, especially in high-risk pregnant women 1.

Management Approach

Severe Hypertension (Emergency)

For BP ≥160/110 mmHg (severe hypertension):

• Immediate intervention required within 30-60 minutes for BP ≥180/110 mmHg 2
• Target BP: Reduce to <160/110 mmHg but not lower than 130/90 mmHg to avoid compromising uteroplacental perfusion 2
• First-line IV medications:
  • Labetalol: 20 mg IV bolus, then 40 mg after 10 minutes, followed by 80 mg every 10 minutes for 2 additional doses (maximum 220 mg)
  • Hydralazine: 5 mg IV bolus, then 10 mg every 20-30 minutes (maximum 25 mg)
  • Nifedipine: 10 mg orally, repeated every 20 minutes (maximum 30 mg) 2, 3

Caution: IV hydralazine is associated with more perinatal adverse effects than other drugs. Sodium nitroprusside should only be used as a last resort due to risk of fetal cyanide poisoning 1.

Non-Severe Hypertension

For persistent BP 140-159/90-109 mmHg:

• ISSHP recommends starting antihypertensives to prevent progression to severe hypertension 1
• Target BP: Diastolic BP of 85 mmHg and systolic BP <160 mmHg (based on CHIPS trial) 1
• Preferred medications:
  • Methyldopa: 250-500 mg twice daily or more frequently
  • Labetalol: 200-800 mg divided twice daily or more frequently
  • Nifedipine XR: 30-60 mg once daily
  • Amlodipine: 5-10 mg once daily 1, 2

Avoid: ACE inhibitors and angiotensin II antagonists are contraindicated in pregnancy due to increased risk of fetopathy 4.

Prevention of Eclampsia

• Magnesium sulfate is recommended to prevent eclampsia in women with preeclampsia 1
• Most beneficial in low and middle-income countries, but selective use is reasonable in high-income settings
• Continue MgSO4 for 24 hours postpartum 1
• Dosing regimens from the Eclampsia and MAGPIE trials should be used 1

Non-Pharmacological Management

• For mild hypertension (140-149/90-95 mmHg), consider non-pharmacological management with close supervision and limitation of activities 1
• Normal diet without salt restriction is advised 1
• Weight reduction is not recommended during pregnancy despite its blood pressure-lowering effect 1

Special Considerations

Timing of Delivery

• The definitive treatment for PIH, especially preeclampsia, is the interruption of pregnancy 5
• Decision between delivery and expectant management depends on:
  • Fetal gestational age
  • Fetal status
  • Severity of maternal condition 6

Postpartum Management

• Monitor BP shortly after birth, again within 6 hours, and continue for at least 24-72 hours postpartum 2
• Follow-up within 7-10 days after discharge 2
• Annual cardiovascular risk assessments recommended lifelong for women with history of hypertensive disorders in pregnancy 2

Monitoring Requirements

• Women with diagnosed gestational hypertension or preeclampsia require close evaluation of maternal and fetal conditions for the duration of pregnancy 6
• Those with severe disease should be managed in-hospital 6
• Each unit should have a protocol for BP management and regular audit of associated pregnancy outcomes 1

Pitfalls and Caveats

• Avoid atenolol due to association with fetal growth restriction related to treatment duration 1
• Avoid using nifedipine with magnesium sulfate due to risk of precipitous BP drop 2
• Diuretics at higher doses should be avoided as they may affect breastmilk production 2
• Don't delay treatment of severe hypertension - it's associated with increased risk of maternal stroke and adverse outcomes for both mother and baby 1