Table 1.

Major bacterial taxa found at each colonization site of reproductive age women, and their impact on fertility, according to the studies discussed in the review. ART = assisted reproductive technique.

	Physiological	Bacterial Vaginosis	Infertility	ART Outcome
Vagina	-dominated by Lactobacillus spp. -Classified into five community state types (CST): CST I (Lactobacillus crispatus predominant), CST II (Lactobacillus gasseri predominant), CST III (Lactobacillus iners predominant), CST IV (non-Lactobacillus spp.). Type IV-A: low proportions of Lactobacillus iners or other Lactobacillus spp., various species of anaerobic bacteria including Anaerococcus, Corynebacterium, Finegoldia, or Streptococcus. Type IV-B: higher proportion of the genus Atopobium, Prevotella, Parvimonas, Sneathia, Gardnerella, Mobiluncus, Peptoniphilus and other taxa. CST V (Lactobacillus jenseri predominant) [28,36,37,38]	-Prevalence of Gardnerella vaginalis, Mycoplasma hominis, Atopobium vaginale and Mobiluncus curtisii [42,43,44,45] -higher bacterial diversity than physiological conditions [29,46]	-(Chlamydia trachomatis) ascending through the cervix [50,51,52,53] -higher percentage of Lactobacillus gasseri, Veillonella spp. and Staphylococci and lower content of Lactobacillus iners and crispatus [57]	-the diversity of bacterial species and the presence of Lactobacilli on the ET day improved the outcome [58]
Uterus	-Lactobacillus iners, Lactobacillus crispatus, Prevotella spp. [61]	-	-Lactobacillus spp. could improve fertility by inhibiting pathogenic bacteria [50,71]	-uterine microbiota lower in Lactobacillus spp., and non-Lactobacillus spp. dominated was associated with a lower ART success [60] and, on the contrary, Lactobacilli were associated with a negative impact ART outcome [62]