What labs should be ordered for a 37-week pregnant woman with cholestasis prior to induction of labor?

Management of Induction of Labor for Cholestasis in Pregnancy at 37 Weeks

Before proceeding with induction at 37 weeks, you must confirm the diagnosis with laboratory testing and determine the bile acid level, as this directly dictates delivery timing and prevents unnecessary preterm delivery. 1

Essential Pre-Induction Laboratory Testing

Order the following labs immediately if not already obtained:

• Serum total bile acids (non-fasting) - This is the most sensitive and specific diagnostic test for intrahepatic cholestasis of pregnancy (ICP), with levels >10 μmol/L considered diagnostic 1, 2
• Liver transaminases (ALT and AST) - Typically elevated in ICP but not required for diagnosis; levels are usually <500 U/L 1, 2
• Complete blood count with platelets - Essential to exclude HELLP syndrome, which carries 1-25% maternal mortality and requires immediate delivery 2
• Coagulation studies (PT/INR) - To assess for coagulopathy before delivery 2
• Bilirubin - Should be <5 mg/dL in ICP; higher levels suggest alternative diagnoses like HELLP or acute fatty liver of pregnancy 2

Critical Decision Point: Bile Acid Level Determines Delivery Timing

The Society for Maternal-Fetal Medicine provides clear, evidence-based delivery timing based on bile acid levels:

• Bile acids ≥100 μmol/L: Deliver at 36 0/7 weeks due to substantially increased stillbirth risk (GRADE 1B) 1
• Bile acids 40-99 μmol/L: Deliver between 36 0/7 and 37 0/7 weeks, with earlier delivery in this range recommended 1
• Bile acids <40 μmol/L: Delivery between 37 0/7 and 39 0/7 weeks is appropriate, with management toward 39 weeks reasonable given low stillbirth risk 1

You should NOT deliver at 37 weeks without laboratory confirmation of elevated bile acids (GRADE 1B) 1

Additional Pre-Induction Considerations

If Bile Acids Are Not Yet Available:

• Use enzymatic bile acid assays for faster results (4 hours to 4 days) rather than mass spectrometry (4-14 days) 2
• If the patient has elevated transaminases or a history of ICP in previous pregnancies, delivery may be reasonable while awaiting bile acid results through shared decision-making 1
• Do not deliver before 37 weeks based on clinical suspicion alone without laboratory confirmation 1, 2

Exclude Life-Threatening Alternatives:

Before attributing symptoms to ICP, you must exclude conditions with significant maternal mortality:

• HELLP syndrome - Check for hemolysis, elevated LDH, and thrombocytopenia 2
• Acute fatty liver of pregnancy (AFLP) - Check glucose and coagulation studies; carries 7-18% maternal mortality 2
• Pre-eclampsia - Assess blood pressure, proteinuria, and symptoms 2

Intrapartum Management

Place the patient on continuous fetal monitoring during labor due to the increased stillbirth risk, as ICP-related fetal demise can occur suddenly even with recent reassuring testing 1

Common Pitfalls to Avoid

• Never induce before 37 weeks without confirmed elevated bile acids - This exposes the neonate to unnecessary prematurity risks 1
• Do not assume normal bile acids exclude ICP if symptoms persist - Pruritus can precede bile acid elevation by several weeks; repeat testing in 1-2 weeks if clinical suspicion remains high 2
• Do not overlook HELLP/AFLP - These conditions can present similarly but require immediate delivery regardless of gestational age 2
• Recognize that normal fetal testing does not eliminate stillbirth risk - ICP-related stillbirth occurs suddenly through a non-placental mechanism, making traditional fetal surveillance less predictive 1

Treatment Considerations

If not already initiated, start ursodeoxycholic acid (UDCA) 10-15 mg/kg/day in divided doses as first-line therapy for maternal symptom relief and potential reduction in adverse outcomes (GRADE 1A) 1, 2