Studies (n) | RR (95% CI) | I2 (%) | Ph* | Ph† | |
All studies | 6 | 1.22 (0.82 to 1.82) | 83 | <0.01 | |
Study quality | |||||
Moderate (4–6) | 1 | 0.69 (0.51 to 0.93) | – | – | 0.008 |
Good (7–9) | 5 | 1.39 (0.91 to 2.13) | 80 | <0.01 | |
Study design | |||||
Case-control | 4 | 1.65 (1.06 to 2.50) | 72 | 0.01 | 0.001 |
Cross-sectional | 2 | 0.72 (0.57 to 0.90) | 0 | 0.68 | |
Geographic location | |||||
Africa | 3 | 1.04 (0.53 to 2.05) | 91 | <0.01 | 0.43 |
Europe | 3 | 1.23 (0.98 to 1.54) | 58 | 0.09 | |
Parity | |||||
Primiparous | 1 | 0.69 (0.51 to 0.93) | – | – | 0.008 |
Primiparous and multiparous | 5 | 1.39 (0.91 to 2.13) | 80 | <0.01 | |
Specialised delivery setting | |||||
Yes | 2 | 1.88 (1.14 to 3.09) | 15 | 0.28 | 0.10 |
No | 4 | 1.05 (0.67 to 1.65) | 87 | <0.01 | |
Adjustment/Matching for confounders | |||||
Maternal age | |||||
Yes | 5 | 1.28 (0.74 to 2.20) | 87 | <0.01 | 0.63 |
No | 1 | 1.10 (0.85 to 1.42) | – | – | |
Parity | |||||
Yes | 4 | 1.36 (0.79 to 2.33) | 88 | <0.01 | 0.42 |
No | 2 | 0.87 (0.63 to 1.19) | 61 | 0.11 | |
Education or socioeconomic status | |||||
Yes | 3 | 0.84 (0.62 to 1.14) | 67 | 0.05 | <0.0001 |
No | 3 | 2.07 (1.51 to 2.83) | 0 | 0.49 | |
Ethnicity | |||||
Yes | 2 | 1.32 (0.41 to 4.23) | 88 | <0.01 | 0.90 |
No | 4 | 1.21 (0.74 to 1.99) | 86 | <0.01 | |
Marital status | |||||
Yes | 1 | 0.76 (0.53 to 1.08) | – | – | 0.05 |
No | 5 | 1.36 (0.85 to 2.18) | 85 | <0.01 |
n denotes the number of studies.
*P for heterogeneity within each subgroup.
†P for heterogeneity between subgroups.