Table 2 Secondary analyses for meta-analyses reporting both continuous and dichotomous outcomes (N = 18)

Bupassiri 2011 [34]

21 (8,319)

65 (16, 114)

0.01

5 (13,638)

0.83 (0.63, 1.09)

0.18

21 (8,319)

0.72 (0.58, 0.89)

< 0.01

Crowther 2010 [35]

4 (417)

75 (−17, 167)

0.11

7 (1,452)

0.84 (0.68, 1.04)

0.12

4 (417)

0.99 (0.88, 1.06)

0.42

Dodd 2010 [36]

2 (282)

−75 (−210, 61)

0.28

1 (49)

0.41 (0.04, 4.20)

0.45

2 (282)

1.33 (0.78, 2.26)

0.29

2/3 primary studies of mean birthweight outcome accessed

Gouin 2011 [37]

18 (6,855)

−441 (−532, −350)

< 0.01

19 (38,796)

2.86 (2.36, 3.48)

< 0.01

18 (6,855)

2.76 (2.12, 3.45)

0.01

Gülmezoglu 2011 [38]

1 (208)

−100 (−240, 40)

0.16

1 (604)

1.38 (0.92, 2.06)

0.12

1 (208)

1.40 (0.87, 2.24)

0.16

Kawai 2011 [39]

13 (35,015)

45 (28, 62)

< 0.01

13 (35,015)

0.92 (0.83, 1.02)

0.09

13 (35,015)

0.82 (0.75, 0.91)

< 0.01

13/15 primary studies accessed

Kenyon 2010 [40]

13 (6,480)

49 (14, 85)

0.01

2 (4,876)

1.00 (0.96, 1.04)

0.94

13 (6,480)

0.99 (0.99, 1.00)

0.53

Ladhani 2011 [41]

4 (880)

−279 (−485, −74)

0.01

2 (26,026)

3.28 (2.25, 4.78)

< 0.01

4 (880)

2.41 (1.42, 4.09)

< 0.01

Lamont 2011 [42]

1 (485)

−12 (−128, 104)

0.89

2 (876)

0.96 (0.62, 1.47)

0.83

1 (485)

1.03 (0.77, 1.38)

0.84

Mathanga 2011 [43]

2 (640)

121 (27, 214)

0.01

2 (624)

0.80 (0.54, 1.18)

0.25

2 (640)

0.75 (0.60, 0.94)

0.01

McDonald 2010 [44]

9 (5,225)

−120 (−248, 6.8)

0.06

9 (5,225)

0.92 (0.72, 1.16)

0.46

9 (5,225)

1.12 (0.99, 1.26)

0.07

9/10 primary studies accessed

Murphy 2011 [45]

8 (179,589)

−121 (−199, −43)

< 0.01

12 (1,110,176)

1.45 (1.21, 1.73)

< 0.01

8 (179,589)

1.46 (1.10, 1.94)

0.01

Reveiz 2011 [46]

3 (237)

15 (−111, 142)

0.81

1 (100)

Not estimated

NA

3 (237)

0.95 (0.59, 1.52)

0.83

Zero cases of LBW in both treatment arms of primary study

Salmasi 2010 [47]

44 (71,663)

13 (−105, 131)

0.83

18 (40,790)

1.09 (0.88, 1.35)

0.44

44 (71,663)

0.98 (0.77, 1.23)

0.85

18/19 primary studies of LBW outcome accessed

Whitworth 2010 [48]

5 (23,213)

11 (−20, 41)

0.49

8 (19,337)

1.04 (0.82, 1.33)

0.73

5 (23,213)

0.97 (0.87, 1.08)

0.56

Wiysonge 2011 [49]

3 (1,809)

68 (19, 118)

0.01

4 (2,606)

0.83 (0.68, 1.01)

0.07

3 (1,809)

0.84 (0.74, 0.95)

0.01

Number of studies (sample size)

Mean difference (g) (95% CI)

P -value

Number of studies (sample size)

OR (95% CI)

P- value

Number of studies (sample size)

Distributional OR (95% CI)

P -value

Pope 2010 [50]

5 (13,955)

100 (73, 128)

< 0.01

8 (Unclear)

1.38 (1.25, 1.52)

< 0.01

5 (13,955)

0.81 (0.76, 0.86)

< 0.01

Pooled published pre-calculated estimates for LBW outcome (that is Log(OR) and SE)

Salvig 2010^a[51]

(Fixed effects model)

4 (1,187)

66 (1.6, 131)

0.04

3 (785)

0.98 (0.66, 1.46)

0.93

4 (1,187)

0.81 (0.65, 1.01)

0.07

Salvig 2010^a[51]

(Random effects model)

4 (1,187)

68 (−75, 212)

0.35

3 (785)

0.95 (0.49, 1.85)

0.88

4 (1,187)

0.79 (0.48, 1.29)

0.34