The pregnancy vaginal microbiota exhibits alterations in association with gravidity, parity, and miscarriage history: a cohort study

Vaginal microbiota plays a critical role in reproductive health, yet the impact of woman’s obstetric history including gravidity, parity and miscarriage history, remains inadequately characterized. We conducted a cohort study to identify microbial biomarkers linked to these factors and pregnancy outcomes. Our primary aim was to characterize pregnancy vaginal microbiota composition and its correlations with gravidity, parity, and miscarriage history. Utilizing high-throughput 16S ribosomal RNA sequencing technology, a description of the taxonomic composition and community structure of vaginal microbiota was conducted among 98 Chinese pregnant women. Clinical data were collected systematically, followed by bioinformatics and statistical analyses to investigate the associations between vaginal microbiota characteristics and gravidity, parity, and miscarriage history. Community state type analysis identified five profiles, with CST III ( Lactobacillus iners -dominated) being most prevalent. Significantly higher prevalence of non- Lactobacillus -dominated CSTs (CST IV) and lower proportion of CST II were found in women with multigravida, multiple deliveries, and miscarriage history. Beta diversity and taxonomic analysis revealed significantly difference among those groups. Significant differences were also found in metabolic pathways, including DNA replication proteins pathway, associated with gravidity and miscarriage. Gravidity, parity, miscarriage history, total protein, and lymphocyte count significantly explained partial variation in microbial community structure. Co-occurrence network analysis highlighted antagonistic interactions between Lactobacillus and opportunistic pathogens. The association of Alloscardovia , Pseudomonas , and Mycoplasmataceae with miscarriage history, as well as the positive correlation between Pseudomonas and premature rupture of membranes, were observed. Gravidity, parity, and miscarriage history are significantly associated with distinct shifts in vaginal microbiota composition and function. This study provides insights into microbial signatures linked to reproductive health and underscores the lasting influence of pregnancy events on the vaginal ecosystem.