Studies (n) | RR (95% CI) | I2 (%) | Ph* | Ph† | |
All studies | 7 | 1.37 (0.67 to 2.78) | 92 | <0.01 | |
Study quality | |||||
Moderate (4–6) | 1 | 0.92 (0.48 to 1.75) | – | – | 0.38 |
Good (7–9) | 6 | 1.47 (0.65 to 3.31) | 93 | <0.01 | |
Study design | |||||
Case-control | 5 | 1.46 (0.55 to 3.91) | 94 | <0.01 | 0.71 |
Cross-sectional | 2 | 1.19 (0.73 to 1.94) | 16 | 0.28 | |
Geographic location | |||||
Africa | 4 | 2.38 (0.82 to 6.89) | 89 | <0.01 | 0.11 |
Europe | 3 | 0.69 (0.23 to 2.05) | 94 | <0.01 | |
Parity | |||||
Primiparous | 2 | 3.46 (0.25 to 47.52) | 96 | <0.01 | 0.36 |
Primiparous and multiparous | 5 | 0.98 (0.49 to 1.94) | 89 | <0.01 | |
Specialised delivery setting | |||||
Yes | 2 | 0.47 (0.31 to 0.70) | 88 | <0.01 | 0.02 |
No | 5 | 2.15 (1.08 to 4.27) | 87 | <0.01 | |
Adjustment/Matching for confounders | |||||
Maternal age | |||||
Yes | 6 | 1.34 (0.51 to 3.54) | 93 | <0.01 | 0.73 |
No | 1 | 1.60 (1.20 to 2.00) | – | – | |
Parity | |||||
Yes | 5 | 1.88 (0.90 to 3.93) | 89 | <0.01 | 0.25 |
No | 2 | 0.60 (0.10 to 3.68) | 94 | <0.01 | |
Education or socioeconomic status | |||||
Yes | 3 | 1.49 (1.19 to 1.86) | 18 | 0.30 | 0.99 |
No | 4 | 1.45 (0.31 to 6.68) | 96 | <0.01 | |
Ethnicity | |||||
Yes | 2 | 1.04 (0.69 to 1.58) | 58 | 0.12 | 0.57 |
No | 5 | 1.51 (0.55 to 4.14) | 94 | <0.01 | |
Marital status | |||||
Yes | 1 | 1.52 (0.81 to 2.86) | – | – | 0.82 |
No | 6 | 1.35 (0.59 to 3.08) | 93 | <0.01 |
n denotes the number of studies.
*P for heterogeneity within each subgroup.
†P for heterogeneity between subgroups.