Objective To determine the early diagnostic value of serum C -reactive protein (CRP)、 total complement( CH50 ) activity and complement 3 (C3) concentration of premature women in the subclinical infection.MethodsSolid phase enzyme linked immunosorbent assay ( ELISA method ) was used for measurements of serum CRP levels. According to modified Mayer simple tubular colorimetric method and simple agar immunodiffusion method, we determined the CH50、C3 concentration respectively.Results Premature women with subclinical chorioamnionitis showed higher serum CRP concentration than that of normal pregnancy women (P<0.01). In the subclinical chorioamnionitis, the more serious the infection, the higher the CRP concentration, while CH50 and C3 concentrations were correspondently decreased. Serum CRP concentration in premature labor was the most sensitive index that suggested subclinical chorioamnionitis. ConclusionsSerum CRP、CH50 and C3 concentrations in premature labor are simple,reliable and accurate indexes for early diagnosis of subclinical infection.