Table 1 study characteristics of included studies

Sammeli West et al. (2020) [42]

Finland

25/197

Survey time:/ Mean age: 31.0 Mean BMI: 25.2 Diagnostic criteria: 2-h 75-g OGTT; at 24–28 weeks

Low

Mahnaz Bahri Khomami et al. (2019) [54]

Australia

34/354

Survey time: 2004–2011 Mean age: 30.3 ± 4.5 Mean BMI: 26.1 ± 5.8; percentage of overweight/obesity patients: (177/354) SEI: 46.3 ± 13.8 Smoking: 5.9% Drinking: 6.8% Diagnostic criteria: WHO criteria (2013)

Low

J-Z Chen et al (2016) [52]

China

208/670

Survey time: 2013.06–2015.06 Mean age: 30.44 ± 3.56 Mean BMI: 24.16 ± 3.20 Menarche age: 13.23 ± 1.52 Primigravida:29.50% Diagnostic criteria: /

Low

Ginevra Mills et al (2020) [45]

Canada

2783/14882

Survey time: 2004–2014 Mean age:/ Mean BMI:/ Smoking: 4.6% Diagnostic criteria: /

High/acceptable

S. Weerakiet et al (2004) [43]

Thailand

8/47

Survey time: 1996.06–2002.05 Mean age: 31.6 ± 4 Mean BMI: 24.0 ± 3 Diagnostic criteria: 3-h 100-g OGTT at 24–28 weeks of gestation, ADA criteria

Low

Shiqiao Hu et al (2021) [26]

China

23/557

Survey time: 2016.01–2019.01 Mean age: 29.67 ± 3.57 Mean BMI: 22.63 ± 3.24 Diagnostic criteria: IADPSG criteria (2011)

High/acceptable

Hexia Xia et al (2017) [41]

China

31/94

Survey time: 2010.01–2014.12 Mean age: /Mean BMI: 23.96 Diagnostic criteria: IADPSG criteria (2011)

Low

Dayan Liu et al (2015) [58]

China

107/690

Survey time: 2012.01–2013.01 Mean age: 29.5 Mean BMI:24.7 Diagnostic criteria: 2-h 75-g OGTT

Low

Congcong Sun et al. (2019) [59]

China

54/114

Survey time: 2016.02–2018.08 Mean age: 29.1 Mean BMI: 23 Diagnostic criteria: 2-h 75-g OGTT at 24–28 weeks; 5.1–10.0–8.5 mmol/L

Low

Xiangzun Li et al (2017) [56]

China

12/35

Survey time: 2015.01–2017.01 Mean age: 31.5 ± 3.6 Mean BMI: 24.6 ± 2.6 Diagnostic criteria: 3-h 75-g OGTT at 24–28 weeks; 5.6–10.3–8.6–6.7 mmol/L

Low

Huizhuo Zhong et al. (2017) [57]

China

57/468

Survey time: 2010.01–2016.10 Mean age: / Mean BMI: /Diagnostic criteria: /

High/acceptable

Marlieke deWilde et al. (2015) [51]

The Netherlands

22/72

Survey time: Mean age: 30.5 Mean BMI: 27.4 Smoking: 9% Diagnostic criteria: ADA criteria (2003)

Low

R Helseth Vanky et al. (2013) [1]

Norway

67/273

Survey time:/ Mean age: 29.4 ± 4.4 Mean BMI: 29.0 ± 7.1 Smoking: 8.50% Diagnostic criteria: WHO criteria

High/acceptable

Guanghui Li et al (2018) [46]

China

75/248

Survey time: 2011–2013 Mean age: 30.43 Mean BMI: 24.60 Diagnostic criteria: FPG ≥ 5.1 mmol/L (92 mg/dL), 1‐hour plasma glucose ≥ 10.0 mmol/L (180 mg/dL), or 2‐hour plasma glucose ≥ 8.5 mmol/L (153 mg/dL)

High/acceptable

V. De Fre`ne et al. (2014) [27]

Belgium

119/200

Survey time: 2000.01–2009.12 Mean age: 28.7 Mean BMI: 25.8 Smoking: 20% Diagnostic criteria: ADA criteria (2014) Primigravida: 78.5% Irregular menstrual cycle: 94.5%

Low

Fatemeh Foroozanfard et al. (2020) [48]

Iran

3/43

Survey time: 2014.04–2016.04 Mean age: 24.58 Mean BMI: 24.20 Diagnostic criteria: /

High/acceptable

R. Bond et al. (2017) [53]

Canada

513/941

Survey time: 1990.01–2007.12 Mean age: /Mean BMI: /Diagnostic criteria:/ Primigravida:66.20%

Low

Mahnaz Ashrafi et al. (2014) [55]

Iran

104/234

Survey time: 2002–2003 Mean age: 29.6 ± 3.9 Mean BMI: 26.1 ± 3.4 Diagnostic criteria: ADA criteria (2005) Menarche age: 13.3 ± 1.5 Irregular mense: 84.60%

High/acceptable

Nadira Sultana Kakoly et al. (2017) [47]

Australia

63/448

Survey time: 1996–2012 Mean age: 36.6 ± 1.43 Mean BMI: 29.2 ± 7.86 SEI: 106 (16.0%, education < 12 y) Smoking: 9.52% Menarche age: 13.3 ± 1.5 Diagnostic criteria: /

Low

Michael Feichtinger et al. (2021) [49]

Austria

4/31

Survey time: 2015.06–2017.09 Mean age: 31.3 Mean BMI: /Diagnostic criteria: IADPSG criteria

Low

M.A. deWilde et al. (2014) [50]

The Netherlands

41/189

Survey time: 2008.04–2012.04 Mean age: 29 Mean BMI: 24 Smoking: 11.64% Diagnostic criteria: ADA criteria (2003)

High/acceptable

Roos N et al. (2011) [44]

Sweden

125/3787

Survey time: 1995–2007 Mean age: /Mean BMI: 24 Smoking: 9.57% Diagnostic criteria: as plasma glucose levels of 12.2 mmol/L or more after oral glucose tolerance test (75 g glucose orally administered and plasma glucose measured after two hours) or fasting blood glucose levels of 7.0 mmol/L or more

High/acceptable