What are the causes of elevated bilirubin in pregnancy?

Causes of Elevated Bilirubin in Pregnancy

Elevated bilirubin in pregnancy is most commonly caused by gallstones (25%) and preeclampsia-related disorders including HELLP syndrome (24%), followed by intrahepatic cholestasis of pregnancy (ICP) (13%), with viral hepatitis no longer being a frequent cause in the United States. 1

Primary Etiologies (in Order of Frequency)

1. Gallstone Disease (25%)

• Most common cause of hyperbilirubinemia in contemporary pregnant populations
• Represents a dramatic shift from historical data when viral hepatitis predominated
• Requires consideration of cholecystectomy, which can be safely performed in any trimester 2

2. Preeclampsia/Eclampsia/HELLP Syndrome (24%)

• Second most common cause
• HELLP syndrome specifically involves hemolysis, elevated liver enzymes, and low platelets
• These conditions require planning for delivery and timely evaluation for possible liver transplantation 2
• Daily aspirin prophylaxis should begin at week 12 of gestation for at-risk patients 2

3. Intrahepatic Cholestasis of Pregnancy (13%)

• Presents with pruritus in second/third trimester
• Bilirubin typically remains <6 mg/dL in ICP 2
• If bilirubin is markedly or persistently elevated in suspected ICP, investigate alternative causes 3
• Diagnosed by serum bile acids >10 μmol/L with pruritus 2

4. Acute Fatty Liver of Pregnancy (AFLP)

• Less common but life-threatening
• Requires urgent delivery and intensive supportive care 4
• May necessitate liver transplantation evaluation 2

5. Hyperemesis Gravidarum (5%)

• Typically causes mild transaminase and bilirubin elevation
• Managed supportively with nutritional intervention 4

6. Viral Hepatitis (6%)

• No longer a common cause in the United States due to vaccination programs and demographic shifts 1
• Still requires exclusion, particularly hepatitis C 3

7. Other Causes to Exclude

• Extrahepatic biliary obstruction (ultrasound evaluation) 3
• Autoimmune hepatitis (check AMA, ANA, SMA) 3
• Pre-existing chronic liver disease 3
• Sepsis 5
• Genetic disorders (e.g., UGT1A1 polymorphisms, Crigler-Najjar syndrome) 6, 7

Critical Clinical Pitfalls

When evaluating elevated bilirubin in pregnancy, the level of bilirubin elevation provides diagnostic clues:

• Bilirubin >6 mg/dL is unusual for ICP alone and should prompt investigation for alternative or concurrent diagnoses 2
• Marked hyperbilirubinemia may indicate AFLP, HELLP syndrome, or underlying genetic disorders 6

Maternal hyperbilirubinemia carries significant fetal risk:

• Increased stillbirths, fetal malformations, neonatal deaths, and small-for-gestational-age births 1
• Maternal bilirubin levels predict both maternal and fetal adverse outcomes 5

Diagnostic Approach

When confronted with elevated bilirubin in pregnancy:

1. Assess timing and symptoms: Pruritus suggests ICP; hypertension/proteinuria suggests preeclampsia spectrum
2. Measure serum bile acids: Essential for ICP diagnosis (>10 μmol/L diagnostic) 2
3. Check complete liver panel: ALT, AST, alkaline phosphatase, GGT 3
4. Evaluate for preeclampsia: Blood pressure, proteinuria, platelet count 3
5. Ultrasound abdomen: Rule out biliary obstruction 3
6. Serologic testing: HCV, autoimmune markers if indicated 3

The combination of ALT, bilirubin, GGT, and alkaline phosphatase can generate a laboratory score that reliably predicts adverse outcomes 3