The effect of total blockage of maternal biliary excretion during the last third of the pregnancy on the maturation of hepatobiliary function was investigated in neonatal rats. Extrahepatic obstruction of the common bile duct on day 14 of pregnancy induced a marked enhancement in serum bilirubin--mainly conjugated bilirubin--and bile acid concentrations as compared with sham-operated pregnant rats. Excretion of bile acids by the kidney was significantly increased, whereas fecal elimination of these compounds was almost abolished. Most of the cholestatic mothers (CMs) (77%) were able to carry pregnancy to term and lactation until weaning (21 days after birth). The body and liver weights of their offspring were lower than for offspring of control healthy mothers in all postnatal periods considered. Serum bile acid concentrations were higher in the fetuses and neonates of CMs. This difference was evident up to 1 week after weaning and disappeared in young adult animals (8 weeks old). When the bile secretion rate was investigated in these animals at 4 or 8 weeks of age, no significant difference was found as far as nonstimulated bile flow and bile acid output was concerned. However, the biliary response to stepwise sodium taurocholate (TC) intravenous infusion showed that 4-week-old neonates of CMs had impaired bile acid secretion. Moreover, the maximal secretion rate (SRmax) for TC was significantly reduced (-30%), whereas the choleretic ability of taurocholate was not modified. This alteration was not selective for bile acids. The SRmax for bromosulfophthalein (BSP) was also significantly lowered (-40%). These dysfunctions were overcome during subsequent development. No impaired biliary response to either TC or BSP infusion was observed at 8 weeks of age. Morphological abnormalities in the canaliculi were found in animals with impaired biliary function. In summary, these results indicate that maternal cholestasis may profoundly but transiently impair the normal liver maturation. The importance of the implications derived from these findings both in the nutrition and management of human neonates demands further evaluation of the hepatobiliary function of babies born after alterations of fetal-maternal bile acid homeostasis, such as in maternal obstetric cholestasis.