Fig. 5: Vaginal microbiota activates complement in women who deliver preterm.

Cervicovaginal concentrations of C3b, C5, and C5a were measured and compared between 12–16 weeks and 20–24 weeks in women who delivered preterm, term without intervention, and at term following intervention (a–c), n = 122. Statistical analysis was performed using a one-sided Wilcoxon matched pairs signed rank test. C3b, C5, and C5a concentrations were also compared between samples taken from women who were classed as CST I with CST II–V (d–f) n = 385 samples from n = 133 women. The Kruskal–Wallis and Dunn’s multiple comparison’s test was used to determine statistical significance. Cervicovaginal concentrations of C3b, C5, and C5a were compared between women who delivered preterm or at term in those who were classed as being Lactobacillus deplete (n = 22), or abundant in either CST III (L. iners) (n = 22) or CST IV (diverse) (n = 15) (g–i). CST IV was subdivided into CST IV-B (n = 8), CSTIV-C1 (n = 1), CSTIV-C2 (n = 1) and CST IV-C3 (n = 5). Statistical analysis was performed using a one-sided Mann–Whitney test. Data are presented as median values and interquartile ranges (25th and 75th percentiles). Source data are provided as a Source Data file.