| Not including current study |  | Including current study | ||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
 | Number of Studies | Random Effects Pooled OR | Lower 95% CI | Upper 95% CI | I2 |  | Number of Studies | Random Effects Pooled OR | Lower 95% CI | Upper 95% CI | I2 |
Overall | 37 | 2.199 | 1.964 | 2.462 | 86.1% | Â | 38 | 2.155 | 1.941 | 2.395 | 86.0% |
Study design | Â | Â | Â | Â | Â | Â | Â | Â | Â | Â | Â |
   Cohort studies | 23 | 2.345 | 2.045 | 2.690 | 89.7% |  | 24 | 2.284 | 2.014 | 2.591 | 89.5% |
   Case-control studies | 14 | 1.933 | 1.517 | 2.464 | 71.0% |  | 14 | 1.933 | 1.517 | 2.464 | 71.0% |
Setting | Â | Â | Â | Â | Â | Â | Â | Â | Â | Â | Â |
   Population-based studies | 11 | 1.674 | 1.549 | 1.809 | 86.7% |  | 12 | 1.664 | 1.553 | 1.785 | 56.0% |
   Hospital-based studies | 26 | 2.677 | 2.146 | 3.339 | 86.8% |  | 26 | 2.677 | 2.146 | 3.339 | 86.8% |
Timing of PP diagnosis | Â | Â | Â | Â | Â | Â | Â | Â | Â | Â | Â |
   Confirmed at CS | 13 | 2.515 | 1.751 | 3.613 | 88.2% |  | 13 | 2.515 | 1.751 | 3.613 | 88.2% |
   Other | 24 | 1.982 | 1.781 | 2.206 | 80.9% |  | 25 | 1.936 | 1.756 | 2.135 | 80.7% |
Inclusion criteria | Â | Â | Â | Â | Â | Â | Â | Â | Â | Â | Â |
   Studies analyzing 2nd births only | 7 | 1.504 | 1.383 | 1.635 | 0% |  | 8 | 1.540 | 1.442 | 1.645 | 0% |
   Other | 30 | 2.462 | 2.138 | 2.835 | 87.6% |  | 30 | 2.462 | 2.138 | 2.835 | 87.6% |
Risk-adjustment | Â | Â | Â | Â | Â | Â | Â | Â | Â | Â | Â |
   Adjusted for age and parity | 14 | 1.648 | 1.515 | 1.792 | 52.3% |  | 15 | 1.642 | 1.524 | 1.769 | 54.1% |
   Unadjusted estimates | 23 | 2.712 | 2.174 | 3.383 | 87.7% |  | 23 | 2.712 | 2.174 | 3.383 | 87.7% |