First Step in Diagnosing Intense Itching in an 8-Month Pregnant Woman
The first step is to perform a detailed skin examination to differentiate scratching lesions (excoriations) from primary skin lesions such as rash, papules, plaques, or vesicles, which distinguishes ICP from other pregnancy-specific dermatoses. 1
Initial Clinical Assessment
Skin Examination (The Critical First Step)
The skin examination is paramount because it immediately separates two distinct diagnostic pathways 1:
- If no primary rash is present (only excoriations from scratching): This suggests ICP and warrants immediate laboratory testing with serum bile acids and liver transaminases 1, 2
- If a visible rash is present: This indicates a dermatologic condition rather than ICP, and diagnosis should be based on rash morphology and distribution 1
The American College of Obstetricians and Gynecologists specifically recommends this detailed skin examination to identify any rash, excoriations, papules, plaques, or vesicles that would distinguish dermatologic conditions from ICP 1
Why This Matters Clinically
Atopic eruption of pregnancy affects approximately 23% of pregnancies and presents with pruritus plus a visible eczematous rash, making it the most common dermatosis of pregnancy 1. Polymorphic eruption of pregnancy is the second most common, characterized by pruritic urticarial papules and plaques on the abdomen and proximal thighs 1. Both conditions present with visible skin changes that differentiate them from ICP 1.
Immediate Next Steps After Skin Examination
If No Rash Present (Suspicion for ICP)
Immediately measure random (non-fasting) total serum bile acids and liver transaminases (ALT/AST) 2. These are the definitive tests:
- Bile acids >10-11 μmol/L are diagnostic for ICP and represent the most sensitive and specific marker 1, 2
- Liver transaminases are typically elevated in most cases (usually <500 U/L) but are not required for diagnosis 2
- Random bile acid levels are acceptable and more convenient than fasting samples, as the difference is clinically insignificant 2
If Rash Present
Diagnose based on rash morphology and distribution, and treat symptomatically with topical corticosteroids and antihistamines 1. ICP is effectively excluded at this time if a primary dermatologic condition explains the symptoms 1.
Critical Pitfalls to Avoid
Never assume ICP is permanently excluded based on one normal bile acid level if pruritus persists, especially at 32 weeks gestation where ICP can still develop 1. Normal bile acids effectively exclude ICP as the primary diagnosis at that moment, but do not rule out the possibility of ICP developing later in pregnancy 1.
Repeat bile acid testing in 1-2 weeks if symptoms persist or worsen despite normal initial results, as pruritus can precede bile acid elevation by several weeks 1, 2. Serial monitoring is warranted if symptoms continue despite normal initial testing, as ICP can develop later in pregnancy 1.
Repeat bile acids urgently if the patient develops 1:
- Worsening pruritus
- Dark urine
- Jaundice
- Elevated liver transaminases
These findings increase suspicion for ICP despite initially normal bile acids 1.
Additional History to Obtain Concurrently
While performing the skin examination, obtain 2:
- Timing and location of pruritus: ICP typically affects palms and soles, worsens at night, and presents in late second or third trimester 2
- Prior pregnancy history: Up to 90% recurrence risk in subsequent pregnancies 2
- Family history: Familial clustering suggests genetic susceptibility 2
- Personal or family history of atopy: Helps differentiate atopic eruption of pregnancy 1
- Recent medication changes: Excludes drug-induced causes 1
What Not to Do
Do not initiate ursodeoxycholic acid without confirmed elevated bile acids 1. Consider only empiric symptomatic treatment with antihistamines while awaiting repeat testing if initial bile acids are normal but symptoms persist 1.
Never deliver before 37 weeks based on clinical suspicion alone without laboratory confirmation of elevated bile acids 2.