There is a hypothesis that the state of a woman’s cervicovaginal microbiome can correlate with the possibility of such obstetric complications as cervical incompetence and preterm birth. This review summarizes the information about the connection between microbiome and cervical incompetence. It turned out that the dominance of Lactobacillus crispatus and possibly Lactobacillus gasseri in the microbiome is associated with full-term pregnancy while the predominance of other types of Lactobacillus and anaerobic bacterias (Gardnerella, Atopobium, Prevotella, Streptococcus, Ureaplasma., Megasphaera, Escherichia, Shigella, etc.) leads to preterm rupture of fetal membranes and preterm birth. We should pay attention to the fact that high concentration of antimicrobial peptides β-defensin-2 even without dominance of L. crispatus is also associated with full-term pregnancy. When studying cervicovaginal and amniotic fluid of woman who had preterm birth, the rise in concentration of inflammatory‐related cytokin, such as IL-2, IL-8, IL-10 etc., is discovered. The change of components of microbiome and the rise of mother’s immune reaction leads to preterm remodeling and softening of cervix. Thus, the early diagnostics of the changes in cervicovaginal microbiome, cervicovaginal and amniotic fluid may predict cervical incompetence and preterm birth.