Why should urine be collected in a patient with severe pre‑eclampsia at 26 weeks gestation?

Why Collect Urine in Severe Pre-eclampsia at 26 Weeks Gestation

Urine collection is essential in severe pre-eclampsia at 26 weeks to quantify proteinuria for diagnostic confirmation, risk stratification, and baseline documentation—not for ongoing monitoring, as proteinuria levels do not predict maternal or fetal outcomes once the diagnosis is established. 1

Primary Diagnostic Purpose

• Confirm the diagnosis of pre-eclampsia by documenting clinically significant proteinuria (≥0.3 g/day or ≥30 mg/mmol protein-to-creatinine ratio) when new-onset hypertension develops after 20 weeks gestation 1
• The International Society for the Study of Hypertension in Pregnancy (ISSHP) recommends using spot urine protein-to-creatinine ratio (UPCR) as the standard method, with a threshold of ≥30 mg/mmol (≥0.3 mg/mg) indicating significant proteinuria 1, 2
• Automated dipstick urinalysis serves as initial screening; if ≥1+ proteinuria (≥30 mg/dL), proceed immediately to quantification with spot UPCR 1, 2

Risk Stratification at Initial Assessment

• Massive proteinuria (>5 g/24h) correlates with more severe neonatal outcomes and earlier delivery, making initial quantification clinically important for counseling and delivery planning 2, 3
• UPCR >900 mg/mmol (or >500 mg/mmol if maternal age >35 years) is associated with worse maternal outcomes 2
• Proteinuria >3 g/L is linked to significantly lower birth weight and earlier onset of disease 3
• Fetal growth restriction and stillbirth incidence is significantly higher when proteinuria exceeds 5 g/L 3

Establishing Baseline for Superimposed Pre-eclampsia

• In women with pre-existing hypertension or chronic kidney disease, baseline proteinuria measurement is critical to distinguish superimposed pre-eclampsia from worsening chronic disease 4
• When pre-existing hypertension is associated with protein excretion ≥3 g/day after 20 weeks gestation, it is classified as 'pre-existing hypertension plus superimposed gestational hypertension with proteinuria' 1

Important Caveats About Proteinuria Monitoring

Do Not Use for Serial Monitoring

• Once pre-eclampsia is diagnosed, repeated measurement of proteinuria is not recommended because the amount of proteinuria does not predict poor maternal or neonatal outcomes and may lead to unindicated preterm deliveries 4, 5
• During conservative management of severe pre-eclampsia, 89% of women show increasing proteinuria, but the degree of increase does not correlate with rates of HELLP syndrome, abruptio placentae, cesarean delivery for fetal distress, or low Apgar scores 6
• The most important factors influencing maternal and neonatal outcome are severity of blood pressures and presence of end-organ damage, not the degree of protein excretion 4

Proteinuria Is Not Required for Diagnosis

• Pre-eclampsia can be diagnosed without proteinuria if new-onset hypertension after 20 weeks is accompanied by thrombocytopenia, renal insufficiency (creatinine >1.1 mg/dL), liver dysfunction (transaminases >2× normal), pulmonary edema, or neurological symptoms (headache, visual disturbances) 1, 2
• Hypertension or proteinuria may be absent in 10-15% of patients with HELLP syndrome and in 38% of patients with eclampsia 5

Practical Collection Recommendations

• Spot UPCR is preferred over 24-hour collection for convenience, improved clinical efficiency, and elimination of collection errors 1
• If 24-hour collection is performed, it should measure creatinine excretion simultaneously to verify adequacy of collection 7
• A 12-hour urine collection (with cutpoint of 150 mg protein) has 92% sensitivity and 99% specificity compared to 24-hour collection and offers a reasonable compromise 8

Maternal Monitoring Algorithm After Initial Assessment

• Twice-weekly blood tests for hemoglobin, platelet count, liver enzymes, renal function, and uric acid are mandatory 1
• Blood pressure monitoring and clinical assessment for clonus, right upper quadrant pain, headache, and visual disturbances should occur at every visit 1
• If proteinuria was initially absent, repeated assessments for new-onset proteinuria are appropriate; however, if proteinuria is already documented, serial quantification adds no clinical value 1, 4

Common Pitfalls to Avoid

• Do not delay delivery decisions based solely on proteinuria levels—delivery indications include repeated severe hypertension despite three antihypertensive classes, progressive thrombocytopenia, abnormal liver/renal tests, pulmonary edema, neurological features, or non-reassuring fetal status 1
• Do not assume that decreasing proteinuria indicates improvement; clinical status and laboratory markers of end-organ dysfunction are far more reliable 6, 5
• Recognize that proteinuria may fluctuate widely hour-to-hour due to the vasospastic nature of pre-eclampsia 5