OBJECTIVE: The purpose of this study was to test the hypothesis that suppressed immune function in the lower genital tract, as represented by decreased concentrations of cervical proinflammatory cytokines early in pregnancy, is a risk factor for clinical chorioamnionitis. STUDY DESIGN: Interleukin-1beta, interleukin-6, and interleukin-8 were measured by enzyme-linked immunosorbent assay in cervical fluid from a cohort of 403 women at 8 to 20 weeks of gestation. RESULTS: Of the 88 women with one low cytokine concentration, 8.0% of the women had clinical chorioamnionitis compared with 4.4% among the 228 women with no low cytokines (adjusted odds ratio, 2.0; 95% CI, 0.7-5.8). Clinical chorioamnionitis occurred in 15 of the 87 women (17.2%), with two or three depressed cytokine concentrations compared with women with no low cytokines (adjusted odds ratio, 5.1; 95% CI, 2.0-13.0). CONCLUSION: Genital tract immune hyporesponsiveness, as represented by low cervical concentrations of multiple cytokines, permits subsequent clinical chorioamnionitis.