Very severe intrahepatic cholestasis of pregnancy contributed to by azathioprine dosing

Very severe intrahepatic cholestasis of pregnancy (ICP) characterised by total serum bile acid (TSBA) >100 umol/L is associated with an increased stillbirth risk of 3.4%. Patients exposed to thiopurines may be at increased risk of ICP. We report a case of a mid-30-year-old primigravida who presented at 27+2/40 with a 7-week history of pruritus and jaundice and was diagnosed with very severe ICP (TSBA=117 µmol/L). She had inflammatory bowel disease, controlled on azathioprine 200 mg daily. Thiopurine metabolites ratio, 6-methylmercaptopurine: 6-thioguanine nucleotide (6MMP:TGN) was 34 at 12/40 and 21 at 27/40. Cessation of azathioprine precipitated a TSBA fall to 31 µmol/L within 7 days. A multidisciplinary plan was made in conjunction with the patient for delivery between 35 and 36 weeks. This case highlights the risks of thiopurine use in pregnancy and supports ceasing azathioprine treatment immediately at the onset of ICP, avoiding TSBA levels rising.