Real-time sonography was used to examine the biliary tracts of 103 pregnant women. Common hepatic duct size, degree of right hydronephrosis, and presence of gallstones were noted. There were three important observations: (1) The top normal size of the common hepatic duct was 5 mm; (2) no correlation was found between common hepatic duct size and stage of pregnancy or degree of right hydronephrosis; and (3) gallstones were incidentally noted in 3.9% of patients.