What causes itching in the third trimester of pregnancy and how is it treated?

Itching in Third Trimester of Pregnancy

The most critical cause of third-trimester itching is intrahepatic cholestasis of pregnancy (ICP), which requires immediate measurement of serum bile acids and liver transaminases because elevated bile acids >100 μmol/L substantially increase stillbirth risk and mandate delivery at 36 weeks. 1

Diagnostic Approach

Immediate Laboratory Evaluation

• Measure serum bile acids and liver transaminases immediately in any pregnant woman presenting with pruritus, as ICP carries significant stillbirth risk and requires specific management 1
• ICP is diagnosed when serum bile acid levels exceed 10 μmol/L in the setting of pruritus, typically during the second or third trimester 2
• Most ICP cases present in the third trimester with mild to moderately elevated AST/ALT (up to 10-20 times upper limit of normal) and total bilirubin <6 mg/dL 2

Key Clinical Features of ICP

• Pruritus predominantly affects palms and soles, worsens at night, and occurs without a rash 3
• If initial bile acid levels are normal but clinical suspicion remains high, repeat testing after excluding other causes including biliary obstruction, viral hepatitis, and chronic liver disease 2
• Approximately 23% of all pregnancies involve pruritus, with most cases having no underlying pathologic process 1

Exclude Other Causes

• Rule out biliary obstruction, viral hepatitis, chronic liver disease, thyroid disorders, renal failure, and drug reactions 2, 3
• Consider pregnancy-specific dermatoses: polymorphic eruption of pregnancy, pemphigoid gestationis, and atopic eruption of pregnancy (these present with rashes, unlike ICP) 4

Treatment Algorithm Based on Bile Acid Levels

First-Line Medical Treatment

• Initiate ursodeoxycholic acid (UDCA) 10-15 mg/kg/day in divided doses for all confirmed ICP cases 2
• UDCA improves pruritus, serum bile acid levels, and liver transaminases, and meta-analyses demonstrate decreased adverse outcomes including preterm birth and stillbirth 2
• This is a GRADE 1A recommendation for maternal symptom relief 1

Additional Pruritus Management

• If UDCA alone is insufficient, add cholestyramine as second-line therapy 2
• Rifampicin can be attempted as third-line treatment for refractory pruritus 2
• Monitor PT regularly if using cholestyramine and supplement vitamin K when prothrombin time is prolonged 2, 1

Non-Pharmacological Measures

• Use emollients to prevent skin dryness, avoid hot baths/showers, apply cooling gels, and keep nails shortened 3

Delivery Timing Based on Risk Stratification

High-Risk: Bile Acids ≥100 μmol/L

• Deliver at 36 0/7 weeks or at diagnosis if after 36 weeks due to substantially increased stillbirth risk (GRADE 1B recommendation) 2, 1
• The European Association for the Study of the Liver confirms stillbirth risk increases after 35 weeks in this group 2

Moderate-Risk: Bile Acids <100 μmol/L

• Deliver between 36 0/7 and 39 0/7 weeks of gestation (GRADE 1C recommendation) 2, 1
• For bile acids <40 μmol/L, individualized management with consideration of delivery at term is reasonable 2

Antenatal Corticosteroids

• Administer antenatal corticosteroids if delivering before 37 0/7 weeks (GRADE 1A recommendation) 1

Critical Pitfalls to Avoid

• Never delay delivery beyond 36 weeks in confirmed ICP with bile acids ≥100 μmol/L, as stillbirth risk increases substantially 1
• Do not perform preterm delivery based on clinical suspicion alone without laboratory confirmation of elevated bile acids 1
• Serum bile acid levels directly correlate with intrauterine fetal demise risk, with highest risk when levels exceed 100 μmol/L 2
• Do not miss vitamin K deficiency in patients on cholestyramine 1

Postpartum Follow-Up

• Pruritus typically resolves after delivery 2
• If pruritus persists beyond 6 weeks postpartum, pursue further evaluation for underlying chronic liver disease 2