What are the diagnostic criteria for preeclampsia?

How to Diagnose Preeclampsia

Preeclampsia is diagnosed by the presence of new-onset hypertension (BP ≥140/90 mmHg) occurring after 20 weeks' gestation PLUS either proteinuria OR evidence of maternal organ dysfunction, with proteinuria no longer being mandatory for diagnosis. 1

Core Diagnostic Criteria

Essential Component: New-Onset Hypertension After 20 Weeks

• Blood pressure threshold: Systolic BP ≥140 mmHg OR diastolic BP ≥90 mmHg
• Must be documented on at least two occasions
• Cannot be diagnosed before 20 weeks' gestation by definition 2, 1

PLUS One of the Following:

1. Proteinuria (present in ~75% of cases)

• Dipstick: ≥1+ on more than one occasion
• 24-hour collection: ≥300 mg/24 hours (gold standard)
• Protein:creatinine ratio: ≥30 mg/mmol 2, 1

Important caveat: While protein:creatinine ratios can screen effectively (≥30 mg/mmol), local validation is required for quantification as results vary by measurement method 2

2. Maternal Organ Dysfunction (when proteinuria absent)

The 2018 ISSHP guidelines modernized the diagnosis by recognizing that preeclampsia can occur without proteinuria. Evidence of ANY of the following organ systems involvement confirms the diagnosis 1:

Renal dysfunction:

• Serum creatinine elevation
• Oliguria

Hepatic involvement:

• Elevated liver enzymes (AST, ALT, LDH)
• Right upper quadrant or epigastric pain

Hematological complications:

• Thrombocytopenia (low platelet count)
• Hemolysis
• Note: The combination of hemolysis, elevated liver enzymes, and low platelets (HELLP syndrome) represents severe preeclampsia, not a separate entity 1

Neurological features:

• New-onset severe headache unresponsive to medication
• Visual disturbances (scotomata, photopsia, cortical blindness)
• Altered mental status
• Stroke

Uteroplacental dysfunction:

• Fetal growth restriction in context of new hypertension 1

Clinical Assessment Algorithm

After 20 Weeks' Gestation - Screen for These Signs/Symptoms:

1. New hypertension (measure BP properly - errors implicated in maternal deaths)
2. New proteinuria
3. Headache or visual disturbances
4. Epigastric pain or vomiting
5. Reduced fetal movements or small-for-gestational-age infant 2

Immediate Action Thresholds:

Arrange immediate admission if:

• Diastolic BP ≥110 mmHg AND proteinuria ≥1+ on dipstick
• Systolic BP ≥170 mmHg AND proteinuria ≥1+ on dipstick
• Diastolic BP ≥90 mmHg AND proteinuria ≥1+ AND any symptoms (headache, visual changes, epigastric pain) 2

Same-day hospital assessment if:

• Diastolic BP ≥90 mmHg with new proteinuria ≥1+
• Systolic BP ≥160 mmHg (even without proteinuria)
• Diastolic BP ≥100 mmHg (even without proteinuria)
• Diastolic BP 90-99 mmHg with any symptoms
• Epigastric pain (even without hypertension/proteinuria) 2

Essential Laboratory Investigations

When a woman presents with new hypertension after 20 weeks without dipstick proteinuria, the following tests are mandatory to exclude preeclampsia (without these, diagnosis is impossible) 1:

1. Complete blood count - hemoglobin and platelet count
2. Liver function - AST, ALT, LDH, bilirubin, albumin, INR
3. Renal function - creatinine, electrolytes, uric acid*
4. Quantified proteinuria - 24-hour urine collection or protein:creatinine ratio

*Uric acid is NOT diagnostic but elevated levels correlate with worse outcomes and should prompt detailed fetal growth assessment 1

Critical Clinical Pitfalls

Edema is NOT diagnostic - it does not predict preeclampsia and weight change does not reliably precede other signs 2

Hyper-reflexia is NOT diagnostic - removed from modern criteria as it's nonspecific, present in many healthy young women, and highly subject to observer interpretation 1

Eclampsia can occur without severe hypertension - 34% of eclamptic women had maximum diastolic BP ≤100 mmHg 2

Blood pressure measurement technique is critical - improper measurement has been implicated in maternal deaths 2

Preeclampsia can progress rapidly - on average, progression to life-threatening complications occurs within 2 weeks of diagnosis; 25-55% of women with severe hypertension and proteinuria required delivery within 48 hours of admission 2

Distinguishing from Other Hypertensive Disorders

• Chronic hypertension: Present before pregnancy or before 20 weeks
• Gestational hypertension: New hypertension after 20 weeks WITHOUT proteinuria or organ dysfunction
• Transient gestational hypertension: New hypertension that resolves without treatment during pregnancy (carries 20% risk of developing preeclampsia) 1

The modern diagnostic approach recognizes preeclampsia as a multisystem disorder where proteinuria, while common, is neither necessary nor sufficient for diagnosis when other organ dysfunction is present.