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Conjugated (Direct) Bilirubin — Pregnancy Reference Values

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Conjugated (Direct) Bilirubin — Serum

Conjugated bilirubin reflects hepatocellular excretion into bile. Unlike total bilirubin, direct bilirubin elevation is more specific for cholestasis or hepatobiliary disease.

Units Nonpregnant Adult 1st Trimester 2nd Trimester 3rd Trimester
mg/dL 0.1 – 0.4 0 – 0.1 0 – 0.1 0 – 0.1
µmol/L 1.7 – 6.8 0 – 1.7 0 – 1.7 0 – 1.7
Direct bilirubin remains low in normal pregnancy. Persistent elevations warrant evaluation for cholestasis, hepatocellular dysfunction, or biliary obstruction.
Pregnancy physiology
  • Direct bilirubin typically stays within the low nonpregnant range.
  • Elevation usually indicates impaired hepatobiliary excretion, not pregnancy physiology.
  • Helpful in differentiating cholestasis from hemolysis or isolated unconjugated hyperbilirubinemia.
Causes of elevated conjugated bilirubin
  • Intrahepatic cholestasis of pregnancy (ICP)
  • Preeclampsia with liver involvement / HELLP syndrome
  • Viral hepatitis (A–E)
  • Biliary obstruction (stones, strictures, PSC/PBC)
  • Drug-induced cholestasis
  • Cirrhosis or infiltrative liver disease
  • Hereditary disorders (Dubin–Johnson, Rotor)
Causes of low or undetectable conjugated bilirubin
  • Normal finding — physiologic
  • No clinical significance unless other LFTs are abnormal
  • Seen in healthy pregnancy and nonpregnant individuals

References

  1. Abbassi-Ghanavati M, Greer LG, Cunningham FG. Pregnancy and laboratory studies: a reference table for clinicians. Obstet Gynecol. 2009;114:1326–31.
  2. Wallach J. Interpretation of Diagnostic Tests. 8th ed. LWW; 2007.
  3. Fischbach FT, Dunning MB. Manual of Laboratory and Diagnostic Tests. LWW; 2004.