Total Bilirubin — Serum
Total bilirubin reflects both conjugated and unconjugated fractions. Pregnancy often results in slightly lower bilirubin levels, particularly in the first trimester. Persistent elevation suggests hepatic dysfunction, cholestasis, or hemolysis.
| Units | Nonpregnant Adult | 1st Trimester | 2nd Trimester | 3rd Trimester |
|---|---|---|---|---|
| mg/dL | 0.3 – 1.3 | 0.1 – 0.4 | 0.1 – 0.8 | 0.1 – 1.1 |
| µmol/L | 5.1 – 22.2 | 1.7 – 6.8 | 1.7 – 13.7 | 1.7 – 18.8 |
Clinical context
Total bilirubin rises when bilirubin production increases (hemolysis), when hepatic uptake or conjugation is impaired, or when biliary excretion is obstructed. Normal pregnancy should not cause significant elevation.
Causes of elevated total bilirubin
- Viral hepatitis (A, B, C), CMV, EBV
- Cholangitis or biliary obstruction
- Intrahepatic cholestasis of pregnancy (ICP)
- Drug-induced cholestasis
- Hemolytic anemia
- Massive hematoma resorption or transfusion
- Inherited disorders (Dubin–Johnson, Rotor, Gilbert)
- Cirrhosis or infiltrative liver disease
- Congestive hepatopathy from right-sided heart failure or PE
Several medications may increase bilirubin: phenytoin, phenothiazines, erythromycin, penicillins, sulfonamides, OCPs, halothane, PAS, isoniazid, methyldopa, indomethacin.
Causes of low bilirubin
Low bilirubin is generally not clinically meaningful and commonly occurs in normal pregnancy due to
hemodilution and increased hepatic clearance.
References
- Abbassi-Ghanavati M, Greer LG, Cunningham FG. Obstet Gynecol. 2009;114:1326–1331.
- Wallach J. Interpretation of Diagnostic Tests. 8th ed.
- Fischbach FT, Dunning MB. Manual of Laboratory & Diagnostic Tests. 7th ed.