Conclusion
Only a small proportion of vaginal microbiome studies reported the presence of GBS during pregnancy. No systematic differences in factors previously known to introduce bias in microbiome studies were associated with the lack of GBS reporting. However, there was considerable heterogeneity in research methods employed across studies. Consideration of less abundant, but clinically meaningful microbes in vaginal microbiome studies may improve our understanding of how the vaginal microbiota influences pregnancy outcomes. GBS was reported in studies across all trimesters of pregnancy using metagenomic methods, although reporting of culture based GBS does not always correlate with metagenomic GBS reporting. Therefore, studies evaluating the presence of GBS may need to adopt both confirmatory testing for GBS via culture and parallel comparison with results obtained from metagenomic/meta-taxonomic approaches.