Abstract
Vaginal microbiota-host interactions are linked to preterm birth (PTB), which continues to be the primary cause of global childhood mortality. Due to population size, the majority of PTB occurs in Asia, yet there have been few studies of the pregnancy vaginal microbiota in Asian populations. Here, we characterized the vaginal microbiome of 2689 pregnant Chinese women using metataxonomics and in a subset (n = 819), the relationship between vaginal microbiota composition, sialidase activity and leukocyte presence and pregnancy outcomes. Vaginal microbiota were most frequently dominated by Lactobacillus crispatus or L. iners, with the latter associated with vaginal leukocyte presence. Women with high sialidase activity were enriched for bacterial vaginosis-associated genera including Gardnerella, Atopobium and Prevotella. Vaginal microbiota composition, high sialidase activity and/or leukocyte presence was not associated with PTB risk suggesting underlying differences in the vaginal microbiota and/or host immune responses of Chinese women, possibly accounting for low PTB rates in this population.
Highlights
There is substantial evidence implicating the pregnancy vaginal microbiota in shaping maternal and neonatal health outcomes[1,2,3].The dominance of the vaginal niche by commensal Lactobacillus species is often considered “optimal” due to their ability to prevent pathogen colonization through competitive exclusion, in part achieved through the production of antimicrobial compounds and production of lactic acid[4,5]
No relationships were observed between vaginal microbiota composition, sialidase activity and/or leukocyte presence, and chorioamnionitis (Supplementary Fig. 7). In this large cross-sectional study of 2646 pregnant Chinese women, the vaginal microbiota in mid-pregnancy was characterized by Lactobacillus spp. dominance and low diversity
Similar results have been reported in small cohort studies of Chinese and Indian women[42,43]. One of these studies examined the vaginal microbiota of 113 Chinese women and reported L. crispatus dominance in 45.1% and L. iners dominance in 31.9% of women sampled at a mean gestation of 17 weeks[42]
Summary
There is substantial evidence implicating the pregnancy vaginal microbiota in shaping maternal and neonatal health outcomes[1,2,3]. The dominance of the vaginal niche by commensal Lactobacillus species is often considered “optimal” due to their ability to prevent pathogen colonization through competitive exclusion, in part achieved through the production of antimicrobial compounds and production of lactic acid[4,5]. Despite the majority of PTBs (60%) occurring in Asia[16], molecular-based characterization of the vaginal microbiota in pregnancy and its relationship with PTB has largely been restricted to Northern American and European populations. Ethnicity is recognized as a potential confounder of the relationship between the vaginal microbiome and PTB, between Caucasian and women of African-descent in North American or European populations[2,9,10,17]
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