Baseline elevations of C-reactive protein (CRP) during pregnancy have been associated with adverse outcomes, including preterm delivery. Acute elevations have also been associated with intrauterine infections. The relationship between chronic, baseline elevations of CRP and histological chorioamnionitis, however, has not previously been explored. A nested case-control study was performed within a prospective observational cohort of low-risk patients seeking prenatal care. CRP was measured from maternal plasma collected before 13 weeks of estimated gestational age. Cases were defined by histological chorioamnionitis, and controls were selected randomly from patients without chorioamnionitis. We identified 36 cases of chorioamnionitis. There were no significant differences (p=0.64) in CRP concentrations between cases and controls. CRP concentrations remained nonsignificant in a logistic regression model that incorporated prepregnancy body mass index, placental weight, race, and gestational age at delivery (p=0.72). We concluded that the development of histological chorioamnionitis is not associated with elevations in maternal plasma CRP earlier in pregnancy.