Abstract: Objectives: To observe the spiral artery transformation and pregnancy outcome of recurrent spontaneous abortion mice treated with Shoutaiwan, explore the mechanism of Shoutaiwan in mice with recurrent spontaneous abortion. Methods: The abortion-prone CBA/J×DBA/2 matings were established as the model of recurrent spontaneous abortion（43 mice） and the nonabortion-prone CBA/J×BALB/c matings were established as the model of normal pregnancy（12 mice）. The pregnant mice of CBA/J×DBA/2 were randomly divided into 4 groups. From the 4th to 9th day of pregnant mice of every group were oral administration in different doses. All pregnant mice were killed on the 14th day of pregnancy. Then counted the embryo absorption to calculate the absorption rate. The incidence of spiral arterial physiological changes in decidual tissue was observed under light microscope. And the diameter of lumen and wall thickness of spiral artery were measured. The ultrastructure of spiral artery in decidual tissue was observed under transmission electron microscope. Results: The embryo absorption rate of the recurrent spontaneous abortion model are higher than that of the normal pregnancy group (29.49% vs. 4.55%, χ2=18.887，P=0.000). The embryo absorption rate of low-dose, middle-dose and high-dose Shoutaiwan groups were significantly decreased than recurrent spontaneous abortion model group (P＜0.05). The spiral artery transformation rate of the recurrent spontaneous abortion model are lower than that of the normal pregnancy group (11.90% vs. 44.68%， χ2=11.522，P=0.001). Shoutaiwan could expand lumen diameter of the spiral artery and attenuate the thickness of spiral arteries wall. Conclusions: Shoutaiwan could promote the spiral artery transformation of recurrent spontaneous abortion mice.

Key words: Shoutai pill, Abortion, habitual, Recurrent spontaneous abortion, Spiral artery