Abstract: Objective:To study the effects of small doses of mifepristone with misoprosto on placental structures and biochemical changes of pregnant women and fetus in induced labor of full-term pregnancy. Methods:40 full-term pregnant women, with indication of induced labor for preventing prolonged pregnancy, were assigned to 2 groups randomly. 20 cases in group A were treated with mifepristone 100mg,po,36 hours latter, with misoprostol 50μg,q3h,pv.The other 20 cases in group B were treated only misoprostol 50μg,q3h,pv.Besides,20 cases without using above drugs were consisted of control group(group C).Placental function,liver function,nephritic function and glucocorticoids were tested in group A,B and C.The placental structures were examined by microscopy and morphome triological feature image analysis.Results:No significant changes were observed in the biochemical tests and placental structures among three groups.Conclusions:It was safe in labor induction according to the result of placental structural examination and blood tests that full-term pregnant women took mifepristone 100mg with small doses of misoprostol.