Medical and family history
Your doctor should ask about your medical and family history to aid diagnosis. If close female family members have been affected by OC, you may be at increased risk.
It is also important to exclude all other possible causes of your itching, such as allergies or eczema (but it is possible to have a skin condition and OC) and liver disease such as primary biliary cirrhosis (PBC) or hepatitis C.
Other signs such as pale stools or dark urine may indicate a problem with your liver, including OC.
Blood tests
Your doctor can diagnose OC from blood tests called liver function tests (LFTs) and a serum bile salt test.
Liver function tests are performed to gain an idea of how your liver is functioning. A number of separate properties of your blood will be examined. Your doctor should use pregnancy-specific reference ranges to interpret your blood test results.
In OC, doctors will be looking for abnormal levels of the liver enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Sometimes levels of another enzyme, gamma-glutamyl transferase (GGT), will also be raised.
The most specific test involves measuring serum bile salts. In most UK hospitals raised levels would be a measurement of greater than 14µmol/L. However some hospitals may ask you to fast before the test. In this case a fasting level of greater than 10µmol/L would support the diagnosis of OC12.
In most women with OC, both ALT and bile salt levels will be raised, but just one may be raised at the first test.
If the tests are within normal limits and you carry on itching, it is important that the tests are repeated.
Unfortunately the serum bile salt test is not available in all hospitals. Your doctor may need to send a sample to another hospital for diagnosis.
Excluding other liver conditions
If LFTs are abnormal, doctors will carry out screening to eliminate other causes, such as viral hepatitis and autoimmune disease, before diagnosing OC.
This may involve an ultrasound scan to look for any sign of liver abnormality. Doctors may also use ultrasound to check for gallstones (see ‘Useful words’ section), as research suggests these occur more often with OC13.
Women with hepatitis C are at increased risk of developing OC during pregnancy. A small number of women with OC may therefore have undiagnosed hepatitis C. If your test results do show that you have viral hepatitis, or another liver condition, you will then be able to be referred to a specialist in liver disease (hepatologist) and receive treatment.
The presence of itching helps to distinguish OC from other liver diseases of pregnancy, such as HELLP syndrome, acute fatty liver of pregnancy or pre-eclampsia (see ‘Useful words’ section)4.
OC is only completely confirmed when symptoms disappear and liver tests go back to normal after delivery2.