Spatial Localization of Eubacterial 16S rRNA in Early Pregnancy Placenta and Decidua.

Bacteria derived from the maternal circulation have been suggested to seed the human placenta during pregnancy leading to development of an intrinsic placental microbiome; however, other data indicates these bacteria are artifactual contaminants. Limited research on the localization of bacteria in human placental tissue is available, which may help differentiate resident placental bacteria from contaminants. This study spatially localizes bacteria in situ in normal late first to early second trimester human placenta by 16S rRNA chromogenic in situ hybridization and demonstrates patterns consistent with both contaminants and intraparenchymal signals. These results suggest that placental microbiome studies may benefit from spatial strategies that can exclude surface contamination.