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Table 1 Characteristics of the included studies

From: Effect of interleukin-6 polymorphism on risk of preterm birth within population strata: a meta-analysis

(a). Characteristics of the studies included for maternal genotype analysis

Author

Year

Country

Populations

PPROM Excluded?

PTB cases group criteria

Case sample size

Control group criteria

Control sample size

Women of European descent

Annells et al

2004

Australia

White

No

GA<35

202

GA≥37

185

Hartel et al

2004

Germany

White

No

GA<37 and VLBW

365

GA≥37

281

Hollegaard et al

2008

Denmark

White

No

GA<37

62

GA≥37

55

Menon et al

2005

TN & PA, USA

White

No

GA<36

101

GA≥37

326

Simhan et al

2003

PA. USA

White

Yes

GA<34

39

GA≥37

110

Stonek et al

2008

Austria

White

No

GA<34

21

GA≥37

1367

Heterogeneous population

Gomez et al

2010

PA, USA

African American, and others

No

GA<37

60

GA≥37

636

Harper et al

2011

USA

White, African American, Asian, and Others

No

GA<28

33

GA≥37

549

Moura et al

2009

Brazil

Mulatto

No

GA<37

111

GA≥37

94

Moura et al

2009

Brazil

Mulatto and White

No

GA<37

80

GA≥37

101

Simhan et al

2003

PA. USA

African American

Yes

GA<34

12

GA≥37

46

Speer et al

2006

IL, USA

White, African American, and Others

No

GA<35

79

GA≥37

80

(b). Characteristics of the studies included for fetal genotype analysis

Women of European descent

Hartel et al

2004

Germany

White

No

GA<37 and VLBW

606

GA≥37

491

Heterogeneous population

Pereyra et al

2012

Uruguay

Uruguayan

No

GA<37

53

GA≥37

56

Speer et al

2006

IL, USA

White, African American, and Others

No

GA<35

78

GA≥37

78

Velez et al

2007

TN & PA, USA

African American

Yes

GA<36

48

GA≥37

257