Objective:To explore fetal protection effect of progesterone combined with lymphocytes immunotherapy(LIT)and its influences on estrogen and progesterone and coagulation indexes in unexplained recurrent spontaneous abortion(URSA).Methods:A total of 110 URSA patients were divided into control group(n=55,progesterone+HCG)and observation group(n=55,progester-one+LIT)according to the different treatment plan.The pregnancy outcomes,improvement of clinical symptoms,progesterone[human chorionic gonadotropin(HCG),progesterone(P),estradiol(E2)],uterine arterial blood flow resistance[peak systolic velocity/end diastolic velocity(S/D),pulsatility index(PI),resistance index(RI)],coagulation indexes[fibrinogen(FIB),D-dimer(D-D),acti-vated partial thromboplastin time(APTT)]and cytokines[interferon-γ(IFN-γ),interleukin-4(IL-4),helper cell subsets(Th1/Th2)]were compared between the two groups.Results:The success rates of fetal protection in observation group was higher than that in control group(83.64％ vs.61.81％,P＜0.05).The disappearance time of symptoms(lumbago,lower abdominal pain,vaginal bleed-ing)in observation group was shorter than that in control group(P＜0.05).Compared with control group,levels of HCG,P,E2,APTT and IL-4 were higher(P＜0.05),while S/D,PI,RI,FIB,D-D,IFN-γ and Th1/Th2 were lower in observation group(P＜0.05).Con-clusion:LIT combined with progesterone can increase success rate of fetal protection in URSA patients,improve clinical symptoms,reg-ulate levels of estrogen and progesterone,coagulation function and immune function.