What are the diagnostic criteria for preeclampsia in a previously normotensive pregnant woman?

Diagnostic Criteria for Preeclampsia

Preeclampsia is diagnosed when new-onset hypertension (≥140/90 mmHg) develops after 20 weeks of gestation in a previously normotensive woman, accompanied by either proteinuria OR evidence of maternal organ dysfunction OR uteroplacental dysfunction. 1

Blood Pressure Requirements

• Hypertension must be ≥140 mmHg systolic OR ≥90 mmHg diastolic, confirmed on two separate occasions at least 15 minutes apart (or immediately in cases of severe hypertension ≥160/110 mmHg) 1
• The hypertension must arise de novo at or after 20 weeks' gestation in a woman with documented normal blood pressure earlier in pregnancy 2, 1
• Blood pressure measurements taken before 12 weeks may not be reliable for establishing baseline normotension, as physiologic first-trimester BP decreases can mask underlying chronic hypertension 2

Proteinuria Criteria (When Present)

Proteinuria is no longer required for diagnosis but when present supports the diagnosis: 1, 3

• Significant proteinuria is defined as >0.3 g/24 hours OR albumin-creatinine ratio ≥30 mg/mmol 1
• A positive dipstick test (≥1+) should prompt quantification using albumin-creatinine ratio or 24-hour urine collection 1
• An albumin-creatinine ratio <30 mg/mmol reliably excludes proteinuria 1
• Proteinuria is present in approximately 75% of preeclampsia cases but does not correlate with outcomes 3

Alternative Diagnostic Criteria (Without Proteinuria)

In the absence of proteinuria, preeclampsia can be diagnosed when gestational hypertension is accompanied by ANY of the following: 1, 3

Maternal Organ Dysfunction:

• Renal dysfunction: Serum creatinine ≥1.1 mg/dL or doubling of baseline creatinine 1, 4
• Hepatic dysfunction: Liver transaminases ≥2 times upper limit of normal 1, 4
• Hematological dysfunction: Thrombocytopenia with platelet count <100,000/μL 1, 4
• Neurological complications: Severe headache, visual disturbances (scotomata, cortical blindness), or eclampsia 1
• Pulmonary edema 1, 3

Uteroplacental Dysfunction:

• Fetal growth restriction 1
• Abnormal umbilical artery Doppler waveform analysis 1
• Intrauterine fetal death 1

Critical Diagnostic Pitfalls to Avoid

• Edema is NOT diagnostic and should not be used as a criterion, as it is not predictive 5
• Hyperreflexia is nonspecific and no longer recommended as a diagnostic criterion 1
• Neither serum uric acid nor the level of proteinuria should be used as indications for delivery 1
• Oliguria was removed as a characteristic of severe disease 6
• Hypertension appearing before 20 weeks typically represents chronic hypertension, not preeclampsia 1

Timing Considerations

• New hypertension before 32 weeks carries a 50% chance of developing preeclampsia 1
• New hypertension at 24-28 weeks is particularly predictive of severe preeclampsia 1
• Preeclampsia can present or worsen postpartum, with 10% of maternal deaths occurring in the postpartum period 4
• Cases have been reported up to 3 months postpartum, though this is rare 6

Biomarker Adjunct

• A sFlt-1/PlGF ratio ≤38 can exclude the development of preeclampsia in the following week when clinically suspected 1

Differential Diagnosis

The following conditions must be distinguished from preeclampsia: 1

• Gestational hypertension without proteinuria or organ dysfunction
• Chronic hypertension (present before 20 weeks or before pregnancy)
• Preeclampsia superimposed on chronic hypertension
• White-coat hypertension (present from early pregnancy) 2