What are the diagnostic criteria and initial management steps for gestational hypertension in a pregnant woman after 20 weeks gestation without prior chronic hypertension or proteinuria?

Gestational Hypertension: Diagnostic Criteria and Management

Diagnostic Criteria

Gestational hypertension is diagnosed when blood pressure reaches ≥140/90 mmHg on at least two separate occasions after 20 weeks of gestation in a previously normotensive woman, without significant proteinuria (≥0.3 g/24h or ≥30 mg/mmol urinary creatinine). 1, 2

Blood Pressure Thresholds

• Mild gestational hypertension: 140-159/90-109 mmHg 1, 2
• Severe gestational hypertension: ≥160/110 mmHg, requiring urgent management 1, 2
• For severe hypertension (≥160/110 mmHg), confirm diagnosis within 15 minutes with repeated measurements 2
• For non-severe hypertension, confirm with repeated readings over several hours on the same visit or on two consecutive antenatal visits 2

Critical Timing

• Hypertension developing before 20 weeks gestation is classified as chronic hypertension, not gestational hypertension 2, 3
• New-onset hypertension at or after 20 weeks is considered gestational hypertension 2, 3

Measurement Recommendations

24-hour ambulatory blood pressure monitoring (ABPM) is superior to conventional office measurements for predicting proteinuria, preterm delivery, and pregnancy outcomes. 1 Normal ABPM values before 22 weeks should be below:

• 24-hour average: <126/76 mmHg 4, 2
• Awake average: <132/79 mmHg 4, 2
• Sleep average: <114/66 mmHg 4, 2

White-coat hypertension (office BP ≥140/90 mmHg but home BP <135/85 mmHg) is not benign and carries increased preeclampsia risk, requiring confirmation with ABPM or home monitoring before diagnosing true hypertension. 4, 2

Initial Management Steps

Baseline Laboratory Evaluation

Immediately assess for preeclampsia features with the following tests: 3

• Complete blood count (to evaluate for thrombocytopenia/HELLP syndrome)
• Liver enzymes (AST, ALT, LDH)
• Serum creatinine and electrolytes
• Uric acid
• Urinalysis with protein-to-creatinine ratio or albumin-to-creatinine ratio

Pharmacologic Treatment Thresholds

The European Society of Cardiology recommends initiating antihypertensive treatment at BP ≥150/95 mmHg persistently, and at BP >140/90 mmHg in women with gestational hypertension, subclinical organ damage, or symptoms. 3, 5

First-Line Antihypertensive Agents

The preferred medications are: 3, 5

• Methyldopa (most evidence, including 7.5-year infant follow-up data)
• Labetalol (comparable efficacy to methyldopa; can be given IV for severe hypertension)
• Nifedipine (calcium channel blocker with extensive safety data)

Contraindicated medications: ACE inhibitors, ARBs, and direct renin inhibitors are strictly prohibited due to severe fetotoxicity. 4, 6 If taken inadvertently in the first trimester, switch immediately and perform close fetal ultrasound monitoring. 4

Monitoring Intensity

Women with gestational hypertension require enhanced surveillance because: 1, 2

• Approximately 20-25% will progress to preeclampsia 2, 3
• Risk depends on gestational age at onset 2
• Home blood pressure monitoring should be implemented 2, 3
• More frequent antenatal visits than routine prenatal care 4, 2

Severe Hypertension Management

For BP ≥160/110 mmHg, this is a hypertensive emergency requiring hospitalization. 5 Immediate treatment is indicated to prevent maternal cerebrovascular events, with IV labetalol as a preferred option. 4, 3

Postpartum Follow-Up

Gestational hypertension typically resolves within 42 days postpartum. 1, 3 Essential follow-up includes:

• Close BP monitoring through 42 days postpartum (10% of maternal deaths from hypertensive disorders occur postpartum) 1
• Reassess proteinuria at 3 months postpartum 4, 3
• If hypertension persists beyond 42 days, reclassify as chronic hypertension 1, 3

Long-Term Cardiovascular Risk

Women with gestational hypertension face significantly increased lifetime cardiovascular risk and require annual medical review. 3 Goals include achieving prepregnancy weight by 12 months postpartum and maintaining healthy lifestyle modifications. 3

Common Pitfalls to Avoid

• Do not assume gestational hypertension is benign: It carries substantial risk for progression to preeclampsia and maternal/fetal complications 1, 2
• Do not rely solely on office BP measurements: Up to 25% may have white-coat hypertension; confirm with ABPM or home monitoring 4, 2
• Do not continue ACE inhibitors or ARBs: These are absolutely contraindicated in pregnancy 4, 6
• Do not delay treatment of severe hypertension: BP ≥160/110 mmHg requires immediate intervention to prevent stroke 5
• Emerging evidence suggests BP elevations of 130-139/80-89 mmHg after 20 weeks may warrant closer monitoring, as these women have 2.4-fold increased risk of developing hypertensive disorders, though current diagnostic thresholds remain at ≥140/90 mmHg 7