What is the diagnostic work‑up for preeclampsia in a pregnant woman after 20 weeks gestation and how should it be managed if diagnosed?

Diagnostic Workup for Preeclampsia

Preeclampsia is diagnosed by new-onset hypertension (≥140/90 mmHg) after 20 weeks gestation accompanied by either proteinuria (≥0.3 g/24h or protein/creatinine ratio ≥30 mg/mmol) OR evidence of maternal organ dysfunction, with proteinuria present in only ~75% of cases. 1

Diagnostic Criteria

Blood Pressure Requirements

• Systolic BP ≥140 mmHg and/or diastolic BP ≥90 mmHg measured after 20 weeks gestation in a previously normotensive woman 1
• Severe hypertension defined as ≥160/110 mmHg requiring urgent treatment 1

Additional Diagnostic Features (At Least One Required if No Proteinuria)

Proteinuria is NOT required for diagnosis - you can diagnose preeclampsia with hypertension plus any of the following: 1

• Renal dysfunction: elevated creatinine, oliguria 1
• Liver involvement: elevated transaminases (AST/ALT), right upper quadrant/epigastric pain 1
• Hematologic complications: thrombocytopenia, hemolysis 1
• Neurological symptoms: severe headache unresponsive to medication, visual disturbances (scotomata), altered mental status 1
• Pulmonary edema 1
• Uteroplacental dysfunction: fetal growth restriction 1

Required Laboratory Workup

All women with new-onset hypertension after 20 weeks must have the following tests performed to evaluate for preeclampsia: 1

Baseline Laboratory Panel

1. Complete blood count: hemoglobin and platelet count 1
2. Liver function tests: AST, ALT, LDH, bilirubin, albumin, INR 1
3. Renal function: serum creatinine, electrolytes, uric acid 1
4. Urinalysis: dipstick screening followed by quantification with protein/creatinine ratio or 24-hour urine collection if positive 1
5. Renal ultrasound if creatinine or urine testing abnormal 1

Important Notes on Laboratory Testing

• Serum uric acid is NOT a diagnostic criterion but elevated levels correlate with worse maternal and fetal outcomes and should prompt detailed fetal growth assessment 1
• Uric acid should NOT be used to determine timing of delivery 1
• HELLP syndrome (hemolysis, elevated liver enzymes, low platelets) is considered part of the preeclampsia spectrum, not a separate disorder 1

Biomarker Testing (PlGF, sFlt-1/PlGF Ratio)

• NOT routinely recommended for diagnosis or to reduce maternal/perinatal morbidity in established or suspected preeclampsia 2
• May have utility in prediction but not standard diagnostic practice 1

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Management of Confirmed Preeclampsia

Initial Assessment and Monitoring

Hospital Evaluation

All women with newly diagnosed preeclampsia should be assessed in hospital initially to establish disease stability 1

• Selected stable patients may transition to outpatient management if reliable for BP monitoring and symptom reporting 1

Maternal Monitoring Requirements

• Blood pressure monitoring: continuous or frequent depending on severity 1
• Clinical assessment: including evaluation for clonus 1
• Laboratory testing: minimum twice weekly (more frequently with clinical changes) including hemoglobin, platelets, liver enzymes, creatinine, and uric acid 1
• Repeat proteinuria assessment if not initially present 1

Fetal Monitoring

• Initial assessment to confirm fetal well-being 1
• Ultrasound evaluation: fetal biometry, amniotic fluid volume, umbilical artery Doppler at diagnosis 1
• Serial surveillance every 2 weeks if initial assessment normal 1
• More frequent monitoring (amniotic fluid and Doppler) in presence of fetal growth restriction 1

Antihypertensive Treatment

Non-Severe Hypertension (140-159/90-109 mmHg)

Oral antihypertensive therapy should be initiated when BP is consistently ≥140/90 mmHg 1

Target diastolic BP: 85 mmHg (systolic 110-140 mmHg in some protocols) 1

First-line oral agents: 1

• Methyldopa
• Labetalol
• Oxprenolol
• Nifedipine

Second/third-line agents: 1

• Hydralazine
• Prazosin

Reduce or cease antihypertensives if diastolic BP falls <80 mmHg 1

Severe Hypertension (≥160/110 mmHg)

Requires urgent treatment in a monitored setting 1

Acceptable agents: 1

• Oral nifedipine (preferred if available)
• IV labetalol
• IV hydralazine
• Oral labetalol if above unavailable 1

Magnesium Sulfate for Seizure Prophylaxis

Indications for MgSO₄: 1

• Preeclampsia with proteinuria AND severe hypertension
• Preeclampsia with neurological signs or symptoms (regardless of proteinuria)
• In resource-limited settings, all women with preeclampsia should receive MgSO₄ 1

Dosing regimen: 1

• Loading dose: 4 g IV or 10 g IM
• Maintenance: 5 g IM every 4 hours OR 1 g/hour IV infusion
• Duration: Until delivery and for at least 24 hours postpartum 1

Delivery Timing

≥37 Weeks Gestation

Delivery is recommended for all women with preeclampsia at ≥37 weeks to reduce maternal morbidity 1, 2

• Trial of labor recommended in absence of contraindications 1

34 to 36+6 Weeks Gestation

Expectant management is recommended for non-severe preeclampsia between 34-36+6 weeks 1

• Delivery at this gestational age reduces severe maternal hypertension but increases moderate prematurity 2
• Do NOT systematically induce labor in this window unless severe features develop 2

<34 Weeks Gestation

Conservative expectant management may be considered in selected patients with close monitoring 1

• Antenatal corticosteroids should be administered to promote fetal lung maturity 3

Indications for Immediate Delivery (Any Gestational Age)

Deliver regardless of gestational age if any of the following occur: 1

• Repeated severe hypertension despite treatment with 3 antihypertensive classes
• Progressive thrombocytopenia
• Progressively abnormal liver or renal function tests
• Pulmonary edema
• Severe neurological features: intractable headache, repeated visual scotomata, seizures (eclampsia)
• Non-reassuring fetal status

Neither serum uric acid nor level of proteinuria should determine delivery timing 1

Important Clinical Pitfalls

• Do NOT attempt to classify as "mild" versus "severe" preeclampsia clinically - all cases may become emergencies rapidly 1
• Plasma volume expansion is NOT recommended routinely 1
• Home BP monitoring is useful as adjunct but not replacement for clinical assessment 1
• Women with gestational hypertension have ~25% risk of progressing to preeclampsia and require close monitoring 1

Postpartum Considerations

• Peak BP occurs days 3-7 postpartum due to fluid mobilization and withdrawal of placental vasodilatory hormones 4
• BP should normalize by 2 weeks postpartum in women without chronic hypertension 4
• Long-term cardiovascular risk is increased - women require lifelong follow-up for hypertension, cardiovascular disease, and diabetes 2, 3