Zhu B, et al. - In 782 normal pregnant women, researchers identified pregnancy-specific normative ranges for several bile acids in the second and third trimester and investigated changes in their concentrations in the period from 12 to 40 weeks gestation. In this cross-sectional study, there were significant concentration differences between the second and third trimesters. Unconjugated bile acids dominate the profile of bile acids in the second trimester; the third trimester is dominated by conjugated bile acids, particularly (taurine-conjugated). In the second and third trimesters, this study sets pregnancy-specific reference intervals for bile acids. This investigation establishes a basis for trimester-specific clinical interpretation of metabolic profiles of bile acids in pregnant women, since the composition of bile acids changes with gestational age.