Fig. 2: Dynamics of Lactobacillus in the maternal vaginal microbiome during pregnancy and the postpartum period, and its potential role in preterm birth.

a Comparison of the relative abundance of bacterial genera in the vaginal microbiome between pregnancy and the postpartum period. b Relative abundances of the top 10 bacterial genera in the vaginal microbiome during pregnancy. c Chao1 and Shannon diversity indices in samples where Lactobacillus was dominant (n = 129) compared with those in which other genera were dominant (n = 33) (Chao1 index: p = 0.00000005, Shannon diversity index: p = 0.0000004). d Longitudinal shifts in the relative abundance of Lactobacillus: sustained high levels from early to late pregnancy (blue), low levels in early pregnancy followed by high levels in late pregnancy (green), and sustained low levels from early to late pregnancy (red). e Comparison of pregnancy continuation beyond 38 weeks between mothers in whom Lactobacillus was dominant during early pregnancy and those in whom other genera were dominant at that time (bar chart; p = 0.0164). Kaplan–Meier curves illustrate pregnancy continuation up to 38 weeks (p = 0.0025). f Comparison of pregnancy continuation beyond 38 weeks between mothers in whom Lactobacillus was dominant during late pregnancy and those in whom other genera were dominant at that time (bar chart; p = 1.0000). Kaplan–Meier curves illustrate pregnancy continuation up to 38 weeks (p = 1.0000). Data are presented as means ± standard errors of the mean. *p < 0.05, ***p < 0.001, Mann–Whitney U test (two-sided) for comparisons of two groups in panels (c), (e), and (f); log-rank test for comparisons of Kaplan–Meier curves in panels (e) and (f).