Risk of Bias Across Studies
The included studies were not originally conducted with a specific focus on GBS. However, most studies were evaluating the composition of the microbiome across pregnancy, or related to birth outcomes that GBS can influence, such as preterm birth (Supplementary Tables S1 andS2 ). There is notable bias against GBS reporting when only genus level data are reported, as well as when studies only speciate lactobacillus. For example, seven studies that did not report GBS only assigned taxonomy to the genus level, 9 only assigned species level assignments for Lactobacillus spp., three only assigned species to Lactobacillus spp. and Gardnerella , and three studies assigned taxonomy to species level, that were included in analysis, but did not report species level results (Table S1 ). Given that species other than lactobacillus can negatively impact vaginal health and birth outcomes, these methods of analysis and reporting contribute to positive bias towards Lactobacillus reporting in the vaginal microbiome literature and negative bias towards other relevant species. Further, four studies only reported the top 15-21 most abundant species or taxa (Table S1 ). Since some vaginal pathogens present in low abundance can cause pregnancy complications the underrepresentation of these pathogens, such as GBS, may indicate bias against reporting of microbes that are not the most abundant taxonomic groups.