Symptomatic and asymptomatic Coxiella burnetii infection during pregnancy have been associated with obstetric complications. We described placental histopathology and clinical outcome of five cases with asymptomatic C burnetii infection during pregnancy and compared these cases with four symptomatic cases from the literature. In contrast with the symptomatic cases, we did not observe necrosis or active inflammation in the placentas of the asymptomatic women. Obstetrical outcome was more favourable in the asymptomatic cases than in the symptomatic cases. Asymptomatic and symptomatic C. burnetii infection during pregnancy are different entities with respect to placental histopathology and the risk of obstetric complications. (C) 2011 Elsevier Ltd. All rights reserved.