Table 1 Quality assessment of the articles reviewed

Alin Akerman 1995 [18]

4

2

5

2

13

Bergvall 2007 [19]

5

2

5

3

15

Cnattingius 2009 [20]

5

2

5

3

15

De Zeeuw 2012 [21]

4

2

5

2

13

Groen-Blokhuis 2011 [22]

3

2

5

2

12

Hestbaek 2003 [23]

4

2

5

2

13

Hultman 2007 [24]

4

2

5

3

14

Gardner 1995 [25]

3

2

5

2

12

Ortqvist 2009 [11]

5

2

5

3

15

Rasanen 2000 [26]

5

2

5

3

15

Suvanand 1997 [27]

3

2

5

3

15

Villamor 2009 [28]

5

2

5

3

15

Williams 1996 [29]

4

2

5

3

14

Yokoyama 2007 [30]

5

2

4

3

14

Median (range)

4 (3-5)

2 (2-2)

5 (4-5)

3 (2-3)

13.5 (12-15)