Proteinuria Assessment and Management in Pregnancy

Screening and Initial Evaluation

A dipstick reading of ≥ 1+ (≈30 mg/dL) on urinalysis during pregnancy is considered abnormal and should trigger confirmatory quantitative testing (spot urine protein‑to‑creatinine ratio or 24‑hour collection) 1.
A positive dipstick (≥ 1+) warrants further quantitative assessment to determine true proteinuria 1, 2, 3.
A negative dipstick result can generally be accepted without additional testing at that encounter 1.

A spot urine protein‑to‑creatinine (PCr) ratio ≥ 30 mg/mmol (0.3 mg/mg) defines abnormal proteinuria 1, 2, 3.
A 24‑hour urine collection showing ≥ 300 mg protein per day is the gold‑standard definition of abnormal proteinuria 1, 4.
The spot PCr ratio is increasingly preferred over a 24‑hour collection because it offers comparable diagnostic accuracy with greater practicality 1, 5.

Protein excretion of 300 mg–5 g per 24 hours meets the diagnostic threshold for preeclampsia when accompanied by new‑onset hypertension after 20 weeks gestation 1.
Proteinuria is sufficient but not required for a pre‑eclampsia diagnosis 1.
Protein excretion > 5 g per 24 hours is linked to more severe neonatal outcomes and earlier delivery 1, 2, 3.
A spot PCr ratio > 900 mg/mmol (or > 500 mg/mmol in patients > 35 years old) correlates with worse maternal outcomes 1, 6.
In cases of nephrotic‑range proteinuria, thromboprophylaxis should be considered 1, 4.

New‑onset proteinuria after 20 weeks gestation, with or without hypertension, should raise suspicion for pre‑eclampsia 1.
In women with chronic hypertension, any new or worsening proteinuria suggests superimposed pre‑eclampsia 1.
Delivery decisions should not be based solely on the degree of proteinuria; blood pressure severity and evidence of end‑organ damage are more predictive of adverse outcomes 1.
If proteinuria is initially documented but subsequent dipstick tests become negative, repeat quantitative testing (spot PCr or 24‑hour collection) to confirm persistence 1, 4.

The European Society of Cardiology defines clinically significant proteinuria in pregnancy as ≥0.3 g/day (≥300 mg/day) in a 24‑hour urine collection or ≥30 mg/mmol urinary creatinine in a spot random urine sample; this threshold separates normal physiological changes from pathological conditions such as pre‑eclampsia. 7, 8

Proteinuria ≥300 mg/day after 20 weeks gestation combined with new‑onset hypertension fulfills the diagnostic criteria for pre‑eclampsia. 7, 8
The presence of hypertension (≥140/90 mm Hg) together with proteinuria ≥300 mg/day defines gestational hypertension with proteinuria (pre‑eclampsia). 7, 8

Pre‑eclampsia affects approximately 5–7 % of pregnancies and is linked to substantial maternal and fetal morbidity. 8, 9