Detection of cytomegalovirus DNA in human placenta

Although human cytomegalovirus (CMV) is one of the most common causes of viral intrauterine and perinatal infection, its distribution in the placenta is poorly understood. The purpose of this study was to determine the frequency of CMV DNA positivity in placentas, to demonstrate the localization of the viral genome, and to identify the clinical features related to placental CMV. A total of 254 placentas from 231 mothers were investigated, and the maternal serum CMV immunoglobulin antibodies were measured. Specimens from both the placental parenchyma and the placental membrane close to the ruptured site in each placenta were examined for the presence of CMV DNA using dot blot hybridization after PCR amplification. None of 57 placentas from seronegative mothers was positive for CMV DNA. Of 197 placentas from seropositive mothers, 60 (30.5%) had CMV DNA in either the parenchyma or the membrane by dot blot analysis. In situ hybridization was carried out on these 60 placentas, and the localization of the viral genome was established in 19; CMV DNA was localized mostly to the villi, including the mesenchyme and trophoblasts, extravillous trophoblasts, and decidual cells. The mean gestational age at delivery was significantly later in the CMV DNA-positive placentas than in the negative placentas (36.9 +/- 5.1 vs 34.7 +/- 6.2 weeks, P = 0.0059). CMV DNA was detected in only 6 of 33 placentas delivered in the second trimester, and all six were associated with either severe maternal nephritis or severe chorioamnionitis. These results suggest that the CMV genome is common in placentas at later gestational ages and in those of earlier gestational ages with certain maternal complications.