Body site-specific micro- and lactobiota in genitourinary infections during pregnancy

Immunological, metabolic, and hormonal changes occur during pregnancy, which can affect the composition and function of the microbiota in diverse body sites. These changes can influence pregnancy outcomes and the health of the mother and baby. We aimed to characterize the microbiota of pregnant women across various body sites and examine the clinical and population-specific factors associated with its composition. The role of lactobacilli in genitourinary infections during pregnancy was analyzed as well.

One hundred and five pregnant women with gestational age between 15 and 20 weeks were recruited from the Women's Clinic of Tartu University Hospital, Estonia. Microbiota samples of the cervix (C, n = 84), vagina (V, n = 85), urine (U, n = 105), mouth (M, n = 85), and rectum (R, n = 84) were analyzed using Illumina NextSeq2000.

Firmicutes was the most common phylum in all investigated locations, with a mean proportion of over 50%. Lactobacillus was the most abundant genus in C, V, and U samples (mean proportions of 76%, 77%, and 59%, respectively), while its mean relative abundance was significantly lower in oral (2.8%) and rectal (6.2%) samples. Lactobacillus iners was the most frequent Lactobacillus species in genitourinary samples, followed by L. unidentified (unid)/crispatus, L. jensenii, and L. gasseri. The mean relative abundance of L. iners and L. unid/crispatus in these locations was relatively equal (36% vs. 32% in C, 35% vs. 33% in V, 25% vs. 27% in U). Higher diversity of total urogenital microbiota was associated with chorioamnionitis and metroendometritis at delivery and genitourinary infections during the second half of pregnancy. The latter was associated with lower Lactobacillus species diversity in C, V, and U samples. These women also had a lower proportion of L. unid/crispatus (in C and V samples) and L. gasseri (in C, V, and U samples), while they had a higher proportion of L. iners in C samples and a higher proportion of other bacteria in C and U samples.

The microbiota of pregnant women is linked to health profile and lifestyle factors and varies in different body regions; however, it is remarkably similar in the cervix and vagina. Higher abundance of Lactobacillus species in mid-pregnancy, particularly L. crispatus and L. gasseri, potentially provides protection against later genitourinary tract infections during pregnancy. This research underscores the importance of microbiota in maternal health and provides a foundation for future studies aimed at developing more effective strategies to support healthy pregnancy.