Objective To explore the cause of bile acid-induced lung injury through investigating the cell apoptosis and the expressions of Capsase-3 in A549 cell of umbilical artery serum in neonates delivered by women with intrahepatic cholestasis of pregnancy. Methods A549 cell was used as target cell.The cultural cells in orifice were divided into control group and intrahepatic cholestasis of pregnancy-serum attacking group.The cells of control group were cultivated with normal nutritive medium.The umbilical arterial blood was cowered from the placental end of pregnant women with intrahepatic cholestasis after the baby had been delivered.Then the serum was gathered, and the cells of the intrahepatic cholestasis of pregnancy-serum attacking group were attacked by intrahepatic cholestasis of pregnancy-serum.After 24 hours, lactate dehydrogenase leakage rate, expression of Caspase-3 and the apoptosis rate of the cells in the 2 groups were detected, respectively. Results The expression of Caspase-3 in A549 cells was observed in the light microscope, and Caspase-3 expre-ssion in the cytoplasm was brown.The lactate dehydrogenase leakage rate[(34.68±0.77)%], the integrate optical density value (981.77±55.21) of the expression of Caspase-3 and the rate of apoptosis[(27.86±0.53)%] of cells in intrahepatic cholestasis of pregnancy group were significantly higher than those of the cells in control group[(17.39±0.66)%, (540.63±38.41), (6.99±0.11)%](t=-45.70, -15.96, -134.41, all P<0.05). Conclusions Umbilical artery serum in neonates delivered by women with intrahepatic cholestasis of pregnancy can induce apoptosis of A549 cells by up-regulating the expression of Caspase-3, and this was the potential machine of bile acid-induced lung injury in newborn infants. Key words: Intrahepatic cholestasis of pregnancy; Serum; Lactate dehydrogenase; Caspase; Apoptosis