Table 1 Characteristics of the 16S rRNA gene sequencing and study cohorts for each dataset included in this meta-analysis

Brown2018 (Br)*

V1-V2

193 (157)

Longitudinal

25 (18–42)

33 (19–51)

43/50/84/0

22 (6–36)

[26,27,28,29]

Fettweis2019 (Fe)

V1-V3

135 (45)

Longitudinal

-

-

0/101/21/13

28 (3–41)

[11, 30]

Kindinger2017 (Ki)

V1-V3

161 (34)

Cross-sectional

25 (18–48)

33 (21–42)

27/30/104/0

16 (16–16)

[10, 31]

Romero2014 (Ro)

V1-V3

90 (18)

Longitudinal

30 (19–54)

25 (17–43)

1/79/5/5

26 (6–41)

[7, 32]

Stafford2017 (St)

V1-V3

133 (26)

Cross-sectional

-

29 (16–42)

4/8/110/11

24 (15–35)

[33, 34]

Digiulio2015 (Di)

V3-V5

40 (11)

Longitudinal

28 (18–50)

30 (19–41)

7/2/22/9

25 (1–40)

[8, 35]

Elovitz2019 (El)

V4

539 (107)

Longitudinal

-

-

0/399/115/25

− (16–28)

[36, 37]

Blostein2020 (Bl)

V4

125 (25)

Cross-sectional

26 (18–37)

28 (18–44)

-

9 (\(<16\))

[38]****

ST_Callahan2017 (SC)

V4

39 (9)

Longitudinal

25 (18–51)

33 (25–42)

4/1/22/12

24 (2–41)

[9, 39, 40]

Subramaniam2016 (Su)

V4

38 (19)

Cross-sectional

25 (16–38)

22 (15–35)

0/18/20/0

− (21–25)

[41, 42]

Tabatabaei2019 (Ta)

V4

450 (94)

Cross-sectional

24 (13–51)

31 (20–44)

19/31/322/78

− (8–13)

[43]****

UAB_Callahan2017 (UC)

V4

96 (41)

Longitudinal

31 (16–73)

27 (17–38)

1/79/9/7

27 (11–41)

[9, 39, 40]