Normal physiologic changes during pregnancy increase renal plasma flow and glomerular filtration rate, which may slightly elevate urinary protein excretion. A 24-hour excretion ≥300 mg remains the diagnostic threshold for proteinuria in preeclampsia.
| Units | Non-pregnant Adult | 1st Trimester | 2nd Trimester | 3rd Trimester |
|---|---|---|---|---|
| mg / 24 hr | <150 | — | 0–255 | 0–254 |
| g / 24 hr | <0.15 | — | 0–0.26 | 0–0.25 |
Causes of High 24-Hour Protein Excretion (Proteinuria)
- Preeclampsia / severe features (most common in pregnancy)
- Functional proteinuria (fever, exercise, high-output cardiac states)
- Orthostatic proteinuria
- Primary glomerular diseases:
- Minimal change disease
- FSGS
- Membranous nephropathy
- IgA nephropathy
- Secondary glomerular disease:
- Diabetic nephropathy
- Lupus nephritis
- HIV-associated nephropathy
- Hepatitis B or C
- Amyloidosis
- Sarcoidosis
- Sickle cell nephropathy
- Alport syndrome
- Tubulointerstitial disorders:
- Acute tubular necrosis (ATN)
- Acute interstitial nephritis
- Fanconi syndrome
- Plasma cell dyscrasias (multiple myeloma, MGUS)
- Heavy metal toxicity
Causes of Low 24-Hour Protein Excretion
- Low serum protein states (malnutrition, liver disease)
- Low muscle mass with low creatinine production
- Early pregnancy before physiologic renal hyperfiltration
- Very dilute urine (excess fluid intake)
- Incomplete 24-hour urine collection
References
- Kratz A, Ferraro M, Sluss PM, Lewandrowski KB. Laboratory reference values. N Engl J Med. 2004;351:1548–1563. PMID: 15470219
- Higby K et al. Normal values of urinary albumin and protein during pregnancy. Am J Obstet Gynecol. 1994;171:984–989. PMID: 7943114
- Mujais SK et al. Marked proteinuria in hypertensive nephrosclerosis. Am J Nephrol. 1985;5:190–195. PMID: 3160240
- Simerville JA. Urinalysis: comprehensive review. Am Fam Physician. 2005;71:1153–1162. PMID: 15791892