Metagenomics of Oral Microbiome During Pregnancy and Postpartum Period

Objectives: Pregnancy represents an altered condition of the body due to the influence of hormonal, metabolic and immunological factors. These alterations may bring about shifts in the microbiota at different habitats of the body. Saliva and the subgingival crevice represents niches of clinical relevance as exacerbated gingival inflammation and periodontitis pose a risk for adverse gestational outcomes. In the present study, we aimed to characterise the oral microbiome to understand the variations in microbial pattern occurring throughout pregnancy and in the postpartum period.
Methods: Subgingival plaque and saliva samples were collected from a cohort of 24 Chinese women during each trimester of their pregnancy and postpartum period. Metagenomics analysis of the samples were performed by sequencing of 16S rRNA gene amplicons using MiSeq platform. Operational taxonomic units were classified using Ribosomal Database Project Classifier against Greengenes database. Metagenomics content was subjected to alpha diversity, beta diversity and relative abundance analysis.
Results: (i) The salivary and subgingival microbiota formed different clusters on Principle Component analysis suggesting the presence of beta diversity between the niches. No distinct grouping of the bacterial communities formed across any trimesters of pregnancy within the sites (ii) Interestingly, the alpha diversity indices, indicating species richness and diversity, was significantly higher in the third trimester for subgingival plaque samples as compared to the second trimester. (iii) The relative abundance of Prevotella species decreased significantly in the postpartum period compared to the third trimester.
Conclusions: This comprehensive study has provided a novel insight into the oral microbial variations during pregnancy and postpartum period. These findings have important implications in the clinical care of pregnant patients. This will also provide a foundation for future studies to explore possible oral-systemic links between oral microbiome and adverse pregnancy outcomes.