Fig. 2

Vaginal progesterone treatment does not alter structure of the vaginal microbiome. a Compared to controls (n = 42), progesterone supplementation (n = 25) had no significant impact upon microbial community profiles with advancing gestation. Similarly, no effect of progesterone treatment upon b the number of species observed or c the corresponding Shannon index of alpha diversity was observed (2-way ANOVA). Fewer women requiring progesterone had a L. crispatus dominated microbiome compared to controls (8/25, 32 vs. 18/42, 43%, P = 0.4); however, progesterone treatment was associated with increased relative L. crispatus abundance with advancing gestation. Advancing gestational age from 18 to 34 weeks was not associated with a significant shift in mean relative abundance of L. iners (d) or L. crispatus (e) in either the controls or progesterone groups (Kruskal-Wallis, Dunn’s multiple comparison)