Oestrogens produce cholestasis by inhibition of bile acid (BA) transport as well as by inhibition of BA synthesis in the liver. The present work was done to clarify the relevance of altered serum BA profile in 28 healthy pregnant women from the 15th to the 40th weeks of pregnancy with increasing oestrogen serum concentrations in comparison to 6 to 8 weeks after delivery with normalized oestrogen status. For the first time 6 free and 10 taurine- and glycine-conjugated BAs were analysed during the normal pregnancy by HPLC with postcolumn derivatisation and fluorescence detection. The primary BAs cholic (CA) and chenodeoxycholic acid (CDCA) as well as their glycine (G-) and taurine (T-) conjugates amount to nearly 70 % of total BAs in serum and were not changed from the 15th to the 40th weeks of pregnancy, but free and G-CDCA increased significantly after delivery. Among the secondary BAs, which were produced in the intestine by bacteria due to dehydroxylation of the primary bile acids CA and CDCA, only taurine-conjugated deoxycholic acid (T-DCA) decreased significantly after delivery. The free BAs, produced by bacteria in the intestine due to deconjugation, were not changed during pregnancy but had doubled in childbed. Some BAs occurred seldom and in small amounts in the serum, but during pregnancy not more frequent than after delivery. Contrary to expectation the increasing oestrogen concentrations did neither enhance total serum bile acids nor change bile acid profile during pregnancy.