BACKGROUND/AIMS: Intrahepatic cholestasis of pregnancy is a specific liver disease of pregnancy of unknown cause. The serum bile acid profile has not been clearly described in this disease and the aim of this study was to investigate the serum conjugated bile acid profile. METHODS: Thirteen patients with intrahepatic cholestasis of pregnancy were studied. Ten patients had been treated with natural progestatin before the onset of pruritus. The glyco- and tauroconjugated bile acids were quantified by high-performance liquid chromatography and direct spectrometric detection at 199 nm. RESULTS: There was no difference between total bile acid concentrations measured by high-performance liquid chromatography (43.5 +/- 22.6 microM, mean +/- S.D.) or by an enzymatic procedure (43.4 +/- 24.6 microM), indicating a low concentration of free bile acids. Primary bile acids represented 88% of total bile acids, i.e. 72.7% for cholic acid and 15.3% for chenodeoxycholic acid. For both cholic and chenodeoxycholic acids glyco- and tauroconjugates were equivalent. Secondary bile acids represented 11.3% of total bile acids. Ursodeoxycholic acid was identified at very low concentrations in only three samples. CONCLUSIONS: We conclude that in intrahepatic cholestasis of pregnancy primary bile acids are very predominant.