What are the latest International Society for the Hypertension in Pregnancy (ISHHP) guidelines for managing hypertension in pregnant women?

Latest ISSHP Guidelines for Managing Hypertension in Pregnancy

Classification System

The ISSHP 2018 guidelines establish a clear classification framework that distinguishes chronic hypertension (present before 20 weeks), gestational hypertension (new-onset after 20 weeks without proteinuria), and preeclampsia (gestational hypertension with proteinuria or other adverse features). 1

The classification includes:

• Chronic hypertension: Hypertension documented before pregnancy or present in the first 20 weeks of gestation, which may be essential or secondary in etiology 1
• Gestational hypertension: New-onset hypertension (BP ≥140/90 mmHg) arising at or after 20 weeks that may be transient (settles with repeated measurements) or persistent 1
• Preeclampsia: Gestational hypertension with proteinuria ≥30 mg/mmol (≥0.3 mg/mg) on protein/creatinine ratio, which can occur de novo or be superimposed on chronic hypertension 1, 2
• White-coat and masked hypertension: Recognized as distinct entities requiring appropriate diagnostic confirmation 1

The ISSHP explicitly recommends abandoning the term "severe preeclampsia" in clinical practice, as it creates confusion and inconsistency in management 1

Blood Pressure Thresholds and Treatment Targets

All pregnant women with BP ≥140/90 mmHg (or ≥135/85 mmHg at home) should receive antihypertensive treatment. 2

• Treatment initiation at these thresholds is based on evidence from the CHIPS trial showing that development of severe hypertension significantly increases adverse outcomes for both mother and baby 2, 3
• Target diastolic BP of 85 mmHg and systolic BP of 110-140 mmHg to balance maternal cardiovascular protection with adequate uteroplacental perfusion 2, 3
• Reduce or cease antihypertensives if diastolic BP falls below 80 mmHg to avoid maternal hypotension and potential placental hypoperfusion 2, 3

BP ≥160/110 mmHg constitutes a hypertensive emergency requiring urgent treatment in a monitored setting due to increased stroke risk 3

First-Line Antihypertensive Medications

Methyldopa, labetalol, and long-acting nifedipine are the three preferred first-line agents due to their established safety profiles and evidence of improved fetal outcomes. 1, 2

Specific considerations:

• Methyldopa: Has the longest safety record with long-term infant outcome data, but should be switched postpartum due to postnatal depression risk 2, 4
• Labetalol: Excellent alternative particularly for women without reactive airway disease, but should not be used concomitantly with calcium channel blockers due to severe hypotension risk 2, 4
• Long-acting nifedipine: Effective for chronic BP control with once-daily dosing advantage; immediate-release formulation is preferred only for acute severe hypertension 2, 4
• Second-line agents: Hydralazine and prazosin may be used when first-line agents are insufficient 3

ACE inhibitors, ARBs, direct renin inhibitors, and mineralocorticoid receptor antagonists are absolutely contraindicated due to fetal teratogenicity and oligohydramnios. 2, 4

Preeclampsia-Specific Management

Women with preeclampsia should be assessed in hospital when first diagnosed, though stable patients may subsequently be managed as outpatients if they can reliably report problems and monitor BP. 2

• Magnesium sulfate should be administered for convulsion prophylaxis in women with preeclampsia who have proteinuria and severe hypertension, or hypertension with neurological signs or symptoms 1, 2
• Delivery should be considered at 37 weeks and zero days gestation, or earlier if any of the following develop: repeated episodes of severe hypertension, progressive thrombocytopenia, progressively abnormal renal or liver enzyme tests, pulmonary edema, or abnormal neurological features 2
• Women with preeclampsia should be considered at high risk for complications for at least 3 days postpartum and monitored closely 2

Prevention Strategies

Aspirin 150 mg/day should be administered to women at increased risk for preeclampsia, starting at 12-16 weeks gestation, to prevent preterm preeclampsia. 2, 4

• Calcium supplementation (1.2-2.5 g/day) should be considered for women at increased risk, especially if dietary intake is likely low (<600 mg/day) 1, 2
• Exercise should be encouraged during pregnancy to maintain health, appropriate body weight, and reduce the likelihood of hypertension 2

Definition of Uncontrollable Hypertension

Uncontrollable BP is defined as inability to control maternal BP despite using ≥3 classes of antihypertensive medications in appropriate doses, which constitutes a maternal indication for delivery regardless of gestational age. 3

Postpartum Management

Antihypertensives should be continued postpartum, with methyldopa switched to an alternative agent due to postnatal depression risk. 2

• NSAIDs should be avoided for postpartum analgesia unless other analgesics are ineffective 2
• Women with preeclampsia remain at high risk for at least 3 days postpartum and require close monitoring 2

Long-Term Cardiovascular Risk

Women with chronic hypertension, gestational hypertension, or preeclampsia have significantly increased lifetime cardiovascular risk and require annual medical review lifelong. 2, 4

• Initial recommendations include achieving prepregnancy weight by 12 months, limiting interpregnancy weight gain, regular BP monitoring, and adopting a healthy lifestyle 2
• Obstetric history should become part of cardiovascular risk assessment in all women 4

Common Pitfalls to Avoid

• Failing to document normal BP before 20 weeks: Without early pregnancy BP documentation, it is impossible to distinguish chronic hypertension masked by first-trimester BP fall from true gestational hypertension 1
• Underestimating transient gestational hypertension: This condition carries a 40% risk of progressing to true gestational hypertension or preeclampsia and requires careful follow-up 1
• Using atenolol: This beta-blocker is associated with intrauterine growth restriction and should be avoided 4
• Inadequate postpartum monitoring: The highest risk period for preeclamptic complications extends at least 3 days postpartum 2