Objective To explore the possible mechanism of Pangshi Antai Decoction（庞氏安胎汤） in treating threatened abortion. Methods A total of 60 first-day pregnant rats were randomly divided into normal group

model group

dydrogesterone group and Pangshi Antai Decoction high

middle

and low dose groups

with 10 rats in each group. The high

middle

and low dose groups were given Pangshi Antai Decoction 89. 6

44. 8

and 22. 4 g/（kg·d）

respectively

from 1 to 12 days of gestation

and the dydrogesterone group was given dydrogesterone tablet solution3. 02 mg/（kg·d） once a day. On the 12 th day of gestation

a rat model of threatened abortion was established by intragastric administration of 3. 75 mg/kg of mifepristone tablet solution except for the normal group. Serum levels of interferon-γ（IFN-γ）

tumor necrosis factor-α（TNF-α）

interleukin-2（IL-2）

interleukin-4（IL-4）

interleukin-6（IL-6）

interleukin-10（IL-10）

and serum levels of estradiol

progesterone

and β-human chorionic gonadotropin（β-HCG） were measured on the 13 th day of gestation in each group of rats. Results Compared with the normal group

the levels of serum IFN-γ

TNF-α

IL-2 increased

IL-4

IL-6

IL-10

estradiol

progesterone

and β-HCG decreased in the model group（P < 0. 05）. Compared with the model group

the levels of IFN-γ and IL-2 were decreased and the level of IL-4 was increased in the middle and high dose groups of Pangshi Antai Decoction（P <0. 05）;the levels of TNF-α were decreased and the levels of IL-6 and IL-10 were increased in the middle and low dose groups of Pangshi Antai Decoction（P < 0. 05）;the levels of serum estradiol

β-HCG and progesterone were increased in each group（P < 0. 05）. The serum levels of estradiol

β-HCG and progesterone in the middle dose of Pangshi Antai Decoction were higher than those in the low dose group and dydrogesterone group（P < 0. 05）.Conclusion Pangshi Antai Decoction can regulate the immune factors of threatened abortion rats

shift the Th1/Th2 value to Th2

and increase the hormone level

so as to achieve the purpose of preserving the fetus.