Table 1.

Genital Microbiota and Association with Infertility.

Genital Tract Area	Findings	Study Population	Author [Reference]
Endometrium	Lactobacillus abundance was 2% in CE and 81% in NCE. L. crispatus was less abundant in CE. Non-lactobacillus taxa were more abundant in CE, Anaerococcus and Gardnerella were negatively correlated with relative abundance of Lactobacillus.	130 infertile women	Liu et al. [32]
	Lactobacillus, Atopobium, Clostridium, Gardnerella, Megasphaera, Parvimonas, Prevotella, Sphingomonas, or Sneathia genera.	35 infertile women (2016); 342 infertile women (2022)	Moreno et al. [31,35]
	Lactobacillus spp. >90% (n = 33), >70% (n = 53). Corynebacterium (n = 40), Bifidobacterium (n = 15), Staphylococcus spp. (n = 38).	70 infertile women	Tao et al. [33]
	Lactobacillus spp. percentage lowest in the IVF patients, followed by non-IVF patients, and highest in healthy volunteers (64% vs. 96% vs. 99.5%). Lactobacillus spp. >90% lowest in IVF group (38% vs. 74% vs. 86%).	102 infertile women	Kyono et al. [34]
Cervix	Infertile women had more Gardnerella in the cervix.	15 infertile women	Wee et al. [39]
	Higher occurrence of Mycobacterium tuberculosis in infertile patients	112 infertile couples	Hok et al. [5]
	Only anaerobic bacteria were found (51% of infertile, 26% of early pregnancy loss, 0% in labor); The largest proportion of patients with both aerobic and anaerobic bacteria was found in the labor group.	47 Women with infertility, early pregnancy loss, and labor	Moberg et al. [44]
	Women examined for infertility had significantly higher levels of anti-chlamydial antibodies.	52 Women with reproductive failure and clinically “inflamed cervixes”, and Infertile women	Koskimies et al. [37]
	E. coli growth in cervical samples was associated with infertility.	288 infertile couples	Mishra et al. [40]
	Women with previous chlamydia infection (ININF > nININF and FSW); Lactobacillus-78.34% in FF, 69% in nININF, 58% in ININF; growth of Gardnerella, Prevotella, and Sneathia (ININF > nININF > FF).	47 [nININF (n = 26), ININF (n = 21)], FSW (n = 54), FF (n = 89)	Graspeuntner et al. [36]
	Chlamydia trachomatis infection 88% in the infertile group vs. 28% in the fertile group.	34 infertile women	Cheong et al. [38]
Vagina	Infertile women had more Ureaplasma in the vagina.	15 infertile women	Wee et al. [39]
	L. iners, L. crispatus, and L. gasseri distinguished idiopathic infertile from other groups. Fusobacteria was present in women with bacterial vaginosis but not in women with idiopathic infertility.	96 women with idiopathic infertility, bacterial vaginosis, non-idiopathic infertility, and healthy women	Campisciano et al. et al. [41]
	Detection of Candida spp. (27%), Enterococcus(23%), E. coli (14%) in infertile women. The percentage of Lactobacillus was relatively low (4%) and asymptomatic vaginosis was present in 28% of women with infertility.	200 (116 women with Infertility and 84 healthy)	Babu et al. [42]
	Lower fecundability was associated with higher Actinobacteria, Gardnerella, L. iners, Fannyhessea vaginalis, and a lower abundance of L. crispatus and L. gasseri. Higher Lactobacillales in the pregnant group.	478 women planning pregnancy	Hong, X. et al. [43]

CE = chronic endometritis, NCE = non-chronic endometritis, L. crispatus = Lactobacillus crispatus, L. iners = Lactobacillus iners, E. coli = Escherichia coli, ININF = infectious infertility, nININF = non-infectious infertility, FSW = female sex workers, FF = Fertile females.