Investigations
1st investigations to order
bile acids
Test
Ordered for any pregnant women with pruritus and no identifiable rash other than excoriations.
Non-fasting total serum bile acid concentrations are recommended to identify peak concentrations, as these are also associated with adverse perinatal outcomes.
There is a marked diurnal variation in bile acid concentrations, with post-prandial elevation, so measurement of non-fasting concentrations can be clinically useful, as the peak serum bile acid concentration is associated with the risk of adverse pregnancy outcome.[2][84][85] Non-fasting bile acid concentrations in the third trimester of uncomplicated pregnancies are higher than laboratory reference ranges, which typically vary between 6 and 15 micromol/L. Using the upper limit of the reference range of 19 micromol/L for normal pregnancy to define ICP was not demonstrated to impact the risk of serious adverse perinatal outcomes in women with mild ICP whose non-fasting peak bile acid concentration was below this concentration.[86]
Bile acid elevations may occur weeks after the onset of pruritus, so regular repeat testing is recommended if symptoms persist. For disease stratification, guidelines suggest monitoring every 1 to 3 weeks, with at least weekly monitoring from 32 gestational weeks given the likely impact on timing of birth and management if severe disease is identified.[79]
Result
laboratory-specific upper end of the normal range, typically ≥10 micromol/L and <40 micromol/L (mild), ≥40 micromol/L and <100 micromol/L (moderate), and ≥100 micromol/L (severe); in non-fasting samples, 19 micromol/L is used as the lower diagnostic threshold
liver function tests
Test
Ordered for any pregnant woman with pruritus to determine degree of liver impairment, although elevations are not required for diagnosis. Weekly testing is recommended from 32 gestational weeks to monitor severity and progress of the disease.[79] Testing is approximately every 2 weeks before this gestation.
A minority of women with ICP experience hyperbilirubinaemia.[10] If bilirubin elevation is marked or persistent, consider investigations to identify the cause.[79]
Result
pregnancy-specific reference ranges should be used; third trimester ranges are alanine aminotransferase 6-32 IU/L, aspartate aminotransferase 11-30 IU/L, bilirubin 3-14 micromol/L (0.18 to 0.82 mg/dL), gamma-glutamyl transferase 3-41 IU/L, alkaline phosphatase 133-418 IU/L
Investigations to consider
coagulation profile
Test
Recommended for any pregnant woman with symptomatic steatorrhoea.
Vitamin K malabsorption may occur in women with steatorrhoea, and this subgroup of women with ICP are likely to benefit from antenatal vitamin K supplementation.
Result
normal or prolonged prothrombin time
hepatitis C virology
Test
There is increased incidence of ICP in those with hepatitis C-induced hepatocellular damage. Performed to exclude hepatitis C.
Result
positive for hepatitis C infection
liver and biliary tract ultrasound
Test
Commonly performed to exclude co-existent liver and biliary tree pathology, particularly if liver dysfunction is particularly elevated or persists postnatally.
Result
ICP has no defined ultrasound features, although gallstones and biliary sludge are commonly seen
full blood count
Test
Anaemia is a prominent feature of liver disease. A full blood count excludes anaemia as an alternative cause of pruritus.
Result
in pregnant women, a haemoglobin level of <110 g/L (<11 g/dL) in the first trimester or <105 g/L (<10.5 g/dL) in the second and third trimesters; postnatally, a haemoglobin level <100 g/L (<10 g/dL) indicates anaemia
auto-antibody tests
Test
A liver autoimmune screen can be performed to identify antibodies associated with autoimmune liver disease. These include anti-smooth muscle and anti-mitochondrial antibodies.
Result
negative for liver-related auto-antibodies
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