Profile of the oral microbiota from preconception to the third trimester of pregnancy and its association with oral hygiene practices

Abstract

Background: The oral microbiota plays vital roles in both oral and systemic health, but limited studies have explored the transition of the female oral microbiota from preconception to pregnancy along with pronounced hormonal fluctuations.

Aim: To characterize the oral microbiota among women in preconception and pregnancy through a prospective study and to explore the associations between the oral microbiota and oral hygiene practices.

Methods: A total of 202 unstimulated saliva samples were collected from 101 women in both preconception and late pregnancy. The oral microbiota was analyzed using 16S rRNA gene sequencing.

Results: The Ace and phylogenetic diversity (PD) index were significantly lower in the third trimester than preconception. The pathogenic taxa Prevotella and Atopobium parvulum were significantly higher during late pregnancy than preconception. Women with overall better oral hygiene practice showed lower richness and diversity in preconception compared to women with poorer oral hygiene practice. The abundance of pathogens such as Dialister during both preconception and pregnancy decreased among women with better oral hygiene practice.

Conclusions: The composition of the oral microbiota changed slightly from preconception to late pregnancy, with more pathogens in saliva samples during pregnancy. Improving oral hygiene practices has the potential to maintain oral micro-ecological balance.

Keywords: 16S rRNA; Oral microbiota; oral hygiene practices; preconception; pregnancy.

Figure 1.

The alpha diversity and beta diversity of the oral microbiota between preconception and the third trimester. (a) Ace index, (b) Shannon index and (c) PD index for preconception and the third trimester during pregnancy. The Ace, Shannon and PD index were compared with the paired t-test. (d) Principal coordinates analysis (PCoA) plot was generated using the weighted UniFrac distances matrix. Each point corresponds to a sample colored by group (preconception and the third trimester during pregnancy). The plotted coordinates explained the percentage of variation. PerMANOVA was performed. R²: variance contribution, the ratio of group variance to the total variance, and the proportion of differences in the original data that can be explained by groups. The larger R² represents the higher explanatory degree of sample differences by groups.

Figure 2.

Distribution of the predominant bacteria at different taxonomic levels and the bacterial difference identified by LefSe analysis of the oral microbiota in preconception and the third trimester. (a) Relative abundance of the predominant oral microbiota at the phylum level, and (b) Relative abundance of the major oral microbiota (> 1%) at the genus level in both preconception and the third trimester. (c) A cladogram for taxonomic representation performed by LefSe analysis showing distinct bacterial taxa between the two periods. Red indicates enrichment in the preconception samples, and green indicates the taxa enriched in the third trimester samples. The diameter of each circle is proportional to the taxon’s abundance. (d) A histogram of the linear discriminant analysis (LDA) scores performed by LefSe analysis representing significant differences in the abundance of the bacterial taxa between the two periods.

Figure 3.

The STAMP results demonstrated distinct species between women who rinsed their mouth after meal and sweets and women who did not during the third trimester of pregnancy. Kruskal-Wallis H-test was performed and Storey FDR was used. Species with q-value < 0.05 was considered significant and are shown here.