Table 1. Characteristics of the studies included in the meta-analysis.
| Study | Year | Ethnicity | Case | Control | No. of case/control | Genotyping method | Age of case/control | BMI of case/control |
| Kwak [28] | 2012 | Korean | OGTT confirmed | Normal fasting glucose | 1399/2025 | Affymetrix array, TaqMan | 32.1/62.5 | 24.2/24.4 |
| Kim [29] | 2011 | Korean | OGTT confirmed | Normal glucose tolerant | 908/966 | TaqMan | 33.2/32.2 | 23.3/21.4 |
| Deng [30] | 2011 | Chinese | GDM patients | Non-diabetic participants | 87/91 | Sequencing | 31.8/29.7 | 23.6/21.5 |
| Heude [31] | 2011 | French | OGTT confirmed | Normal glucose tolerant | 109/1571 | TaqMan | NA/NA | NA/NA |
| Wang [32] | 2011 | Chinese | OGTT confirmed | Normal glucose tolerant | 705/1029 | TaqMan | 32.0/30.0 | 21.7/21.5 |
| Pappa [33] | 2011 | Greek | GDM per IGDW criteria | Normal glucose tolerant | 148/107 | RFLP | 32.5/26.7 | 26.0/24.3 |
| Papadopoulou [34] | 2011 | Swede | OGTT confirmed | Normal glucose tolerant | 803/1110 | TaqMan | NA/NA | NA/NA |
| Shin [35] | 2010 | Korean | OGTT confirmed | Healthy | 930/628 | TaqMan | 33.2/NA | 23.3/NA |
| Cheng [36] | 2010 | Chinese | OGTT confirmed | Normal glucose tolerant | 55/173 | RFLP | 27.0/29.6 | NA/NA |
| Kwak [37] | 2010 | Korean | OGTT confirmed | Normal fasting glucose | 869/632 | TaqMan | 27.9/64.7 | 23.1/23.3 |
| Santos [38] | 2010 | Euro-Brazilian | GDM per ADA criteria | Healthy | 150/600 | RFLP | 31.7/24.9 | 33.5/24.8 |
| Zhou [39] | 2009 | Chinese | OGTT confirmed | Normal glucose tolerant | 520/916 | RFLP | 32.5/30.7 | 21.4/21.4 |
| Cho [40] | 2009 | Korean | OGTT confirmed | Normal fasting glucose | 868/632 | TaqMan | 32.0/64.7 | 23.1/23.3 |
| Zhu [41] | 2009 | Chinese | GDM patients | Non-diabetic participants | 179/180 | RFLP | 28.1/27.4 | 24.6/23.4 |
| Lauenborg [14] | 2008 | Dane | OGTT confirmed | Normal glucose tolerant | 276/2383 | TaqMan | 43.1/45.2 | 28.9/25.0 |
| Shaat [42] | 2007 | Swede | OGTT confirmed | Non-diabetic participants | 637/1232 | TaqMan | 32.3/30.5 | NA/NA |
| Tok [43] | 2006 | Turkish | OGTT confirmed | Normal glucose tolerant | 100/62 | RFLP | 33.5/31.6 | 26.6/23.0 |
| Shaat [44] | 2006 | Swede | OGTT confirmed | Non-diabetic participants | 641/1229 | RFLP | NA/NA | NA/NA |
| Shaat [45] | 2005 | Swede | OGTT confirmed | Normal glucose tolerant | 588/1180 | TaqMan | 32.2/30.5 | NA/NA |
| Shaat [46] | 2004 | Swede | OGTT confirmed | Normal glucose tolerant | 500/550 | RFLP | 32.3/NA | 30.1/NA |
| Chiu [47] | 1994 | American | OGTT confirmed | Non-diabetic participants | 174/99 | SSCP | 28.3/22.1 | 33.9/22.5 |
| Unpublished data | / | Chinese | OGTT confirmed | Normal glucose tolerant | 50/50 | RFLP | 30.5/28.8 | 31.0/27.9 |
OGTT: Oral Glucose Tolerance Test, IGDW: International Gestational Diabetes Workshop, ADA: American Diabetes Association, NA: Not Available.