Table 1

Principal characteristics of selected meta-analyses and the adjustment performed according to the "trim and fill method"

Meta-analysis
Number of trials
Estimated number of missing studies
Model of Effect used
Original combined effect estimates
Adjusted effect estimates
Year of last trial included

Hofmeyr 18
12
0
Fixed
0.35 (0.22–0.56)
Unchanged
1999
Smaill 19
83
18
Random
0.39 (0.35–0.43)
0.42 (0.37–0.47)
2001
Hopkins 14
14
7
Fixed
0.92 (0.70–1.23)
0.57 (0.45–0.73)*
1993
Hopkins 20
11
3
Fixed
1.08 (0.74–1.58)
0.96 (0.68–1.36)
1996
Smaill 21
13
0
Fixed
0.24 (0.19–0.32)
Unchanged
1987
Kenyon 22
13
1
Fixed
0.90 (0.74–1.10)
0.91 (0.74–1.11)
2001
McDonald 23
13
2
Fixed
0.87 (0.74–1.02)
0.92 (0.78–1.07)
2003
Abalos 24
22
1
Fixed
0.75 (0.47–1.19)
0.73 (0.46–1.15)
1995
Knight 25
37
14
Fixed
0.87 (0.80–0.94)
0.91 (0.84–0.99)
1999
King 26
11
1
Fixed
1.49 (0.67–3.34)
1.35 (0.62–2.95)
2002
Atallah 27
11
5
Random
0.35 (0.20–0.60)
0.50 (0.32–0.78)
2001
Martin-Hirsch 13
11
3
Fixed
0.28 (0.25–0.31)
0.27 (0.25–0.30)
1994
Thacker 28
10
5
Fixed
1.39 (1.21–1.59)
1.17 (1.04–1.33)
1993
Hodnett 15
15
5
Fixed
0.91 (0.83–0.99)
0.94 (0.86–1.03)*
2002
Cheng 16
10
1
Fixed
0.63 (0.44–0.92)
0.70 (0.49–1.00)*
2002
Crowley 29
19
3
Fixed
0.20 (0.06–0.70)
0.25 (0.08–0.73)
1992
Oates-Whitehead 30
14
0
Fixed
1.05 (0.83–1.34)
Unchanged
2002
Hodnett 31
13
2
Fixed
0.99 (0.90–1.09)
0.98 (0.89–1.08)
2001
Carroli 32
10
2
Fixed
0.81 (0.70–0.93)
0.83 (0.72–0.95)
1998
Johanson 33
12
2
Fixed
0.59 (0.51–0.68)
0.60 (0.52–0.69)
1996
Hofmeyr 34
25
7
Random
0.65 (0.58–0.73)
0.72 (0.64–0.81)
2003

* Conclusion is possibly affected by publication bias

Souza et al. Reproductive Health 2007 4:3   doi:10.1186/1742-4755-4-3