What are the diagnostic criteria for pre-eclampsia?

Diagnostic Criteria for Pre-eclampsia

Pre-eclampsia is diagnosed as new-onset hypertension (≥140/90 mmHg) after 20 weeks of gestation accompanied by at least one of the following: proteinuria, renal insufficiency, liver involvement, neurological complications, hematological complications, or uteroplacental dysfunction. 1

Definition and Core Diagnostic Elements

Hypertension Criteria

• Blood pressure ≥140/90 mmHg on at least two separate occasions, at least 15 minutes apart 2
• Must be new-onset after 20 weeks of gestation in previously normotensive women 1
• Severe hypertension is defined as SBP ≥160 mmHg or DBP ≥110 mmHg 2

Plus at least ONE of the following:

1. Proteinuria:

   • ≥300 mg in 24-hour urine collection 2
   • Protein-to-creatinine ratio ≥30 mg/mmol in random sample 2
   • Dipstick reading ≥1+ (300 mg/L) requiring confirmation with quantitative methods 2

2. Maternal Organ Dysfunction (in absence of proteinuria) 2:

   • Renal insufficiency: Serum creatinine ≥1.1 mg/dL or doubling of baseline value 2
   • Liver involvement: Elevated transaminases (≥2× normal) 2
   • Neurological complications: Severe headache, visual disturbances, eclampsia 1
   • Hematological complications: Thrombocytopenia (<100,000/μL) 2
   • Pulmonary edema 2

3. Uteroplacental Dysfunction:

   • Fetal growth restriction 2
   • Abnormal umbilical artery Doppler waveform 2

Severe Features of Pre-eclampsia

Pre-eclampsia with severe features is diagnosed when any of the following are present:

• Severe hypertension (SBP ≥160 mmHg or DBP ≥110 mmHg) despite antihypertensive therapy 2
• Platelet count <100,000/μL 2
• Liver transaminases elevated to twice normal concentration 2
• New-onset renal insufficiency (creatinine ≥1.1 mg/dL) 2
• Pulmonary edema 2
• New-onset cerebral or visual disturbances 2
• Severe persistent right upper quadrant or epigastric pain unresponsive to medication 2

Important Clinical Considerations

Timing

• Pre-eclampsia occurs after 20 weeks of gestation 1
• Can be classified as preterm (<37 weeks), term (≥37 weeks), or postpartum 3

Risk Assessment

High-risk factors requiring early specialist referral (before 20 weeks) 2:

• Previous pre-eclampsia
• Multiple pregnancy
• Pre-existing hypertension
• Pre-existing renal disease
• Pre-existing diabetes
• Presence of antiphospholipid antibodies
• Two or more moderate risk factors

Diagnostic Pitfalls to Avoid

1. Do not rely solely on urine dipstick:

   • Dipstick screening alone is not reliable and should not be used to diagnose proteinuria 4
   • Positive dipstick tests (≥1+) should be confirmed with quantitative methods 2

2. Recognize that proteinuria is not mandatory:

   • Recent guidelines no longer require proteinuria for diagnosis if other signs of organ dysfunction are present 5
   • However, in clinical practice, most patients with gestational hypertension are diagnosed with pre-eclampsia based on proteinuria 4

3. Be aware of superimposed pre-eclampsia:

   • In women with pre-existing hypertension or renal disease, diagnosis is based on worsening hypertension or new-onset proteinuria 2
   • For women with pre-existing proteinuria, diagnosis is based on worsening proteinuria or other signs of organ dysfunction 2

4. Consider biomarker testing when available:

   • A soluble fms-like tyrosine kinase (sFlt)-to-placental growth factor (PlGF) ratio ≤38 can help exclude the development of pre-eclampsia in the next week when clinically suspected 2

Monitoring and Assessment

When pre-eclampsia is diagnosed, comprehensive assessment should include:

• Complete blood count (focusing on platelet count)
• Liver enzymes and function tests
• Serum creatinine and electrolytes
• Urinalysis and protein quantification
• Fetal assessment (biometry, amniotic fluid, umbilical artery Doppler) 1

Regular monitoring of blood pressure and proteinuria throughout pregnancy is essential for early detection, particularly in high-risk women 1. The management approach should focus on preventing progression to severe disease and timing delivery appropriately to minimize maternal and fetal morbidity and mortality.