Identification of intracellular bacteria in the basal plate of the human placenta in term and preterm gestations

Abstract

Objective Bacteria have been identified in different regions of the placenta. Here, we tested the hypothesis that the maternal basal plate of the placenta harbors microbes which may be associated with adverse pregnancy outcomes. Study Design We performed a cross-sectional study of pregnancies from a single tertiary care hospital. Maternal medical and obstetric characteristics were obtained and pregnancies followed prospectively for outcomes and placental collection. After delivery, systematic random sampling of the placental basal plate was performed. Paraffin sections of basal plates were stained with four histological stains and scored for morphological evidence of bacteria. Results Of 195 total patients in the study, Gram positive and negative intracellular bacteria of diverse morphologies were documented in the basal plates of 27% of all placentas. 35% of the patients delivered preterm. No difference was noted between placental basal plates from preterm or term gestations. Intracellular bacteria were found in the placental basal plates of 54% spontaneous preterm deliveries before 28 weeks, and in 26% of term spontaneous deliveries (p=0.02). Intracellular bacteria were also documented in placentas without clinical or pathologic chorioamnionitis. Conclusions 27% of placentas demonstrated intracellular bacteria in the placental basal plate using morphological techniques. Thus, the maternal basal plate is a possible source of intrauterine colonization and placental pathological examination could include examination for bacteria in this important maternal fetal interface.