Is there an association between placental inflammatory lesions and vaginal microbiota in preterm labour? A case control study

Background: Preterm birth continues to be a significant contributor to neonatal mortality and morbidity despite diverse unique interventional strategies. There is need for better understanding of differences and influences of the now characterized vaginal microbiome on terminal inflammatory effects in the uterine microenvironment in term and preterm labour to improve on current strategies. How the existence of a postulated placenta microbiome also affects this understanding should be considered. Objectives: The aim of this study was to explore the association between the maternal vaginal microbiota and placental inflammatory lesions in preterm labour and to determine the presence of a placenta microbiome. Methods: In this nested study, we enrolled 36 case and control placentas in a 1:1 ratio matched for age and parity from women delivering preterm between 26 to 36 weeks gestation. The profile of bacteria in the vaginal tract and placenta was characterized and compared through 16S rRNA sequencing. All histologic inflammatory lesions were graded and staged as per recommended latest consensus guidelines on reporting placental lesions. Results: Preterm placentas were associated with greater rates of inflammation (43.3%) compared to term placentas (23.3%). Acute histologic chorioamnionitis accounted for the greatest proportion with higher rates in preterm (33.3%) than term placentas (6.67%). Placenta microbial samples had a sequence read success rate of only 5.7% bearing similarity to oral, environmental and vaginal tract bacteria. Conclusion: (1) Acute histologic chorioamnionitis was associated with preterm labour. (2) There is lack of evidence to support the existence of a placenta microbiome