Table 2.
Results of subgroup analyses.
| Factor | Number of studies | OR (95% CI) | P Value | I2(%), p Value* |
|---|---|---|---|---|
| Study type | ||||
| Case-control | 4 | 1.69 (0.99 to 2.88) | 0.054 < 0.001 | 62.1, 0.048 |
| Cohort + Nested case-control | 4 | 1.33 (1.14 to 1.54) | <0.001 | 0.0, 0.464 |
| Exposures | ||||
| Psychological stress | 3 | 1.80 (1.01 to 3.19) | 0.045 | 49.5, 0.138 |
| Life events | 2 | 1.85 (0.86 to 3.97) | 0.116 | 58.1, 0.123 |
| Work stress | 3 | 1.27 (1.10 to 1.47) | 0.001 | 0.0, 0.911 |
| Control (Miscarriage vs) | ||||
| Live birth | 2 | 2.82 (1.64 to 4.86) | <0.001 | 0.0, 0.765 |
| Ongoing pregnancy | 5 | 1.33 (1.12 to 1.57) | 0.001 | 0.0, 0.485 |
| Undefined | 1 | 1.28 (1.05 to 1.57) | 0.016 | — |
| Quality of studies | ||||
| Low | 2 | 1.73 (0.85 to 3.51) | 0.130 | 77.6, 0.034 |
| High | 6 | 1.38 (1.13 to 1.70) | 0.002 | 21.7, 0.270 |
| With/without adjusted confounders | ||||
| With | 7 | 1.34 (1.16 to 1.54) | <0.001 | 9.2, 0.358 |
| Without | 1 | 2.67 (1.39 to 5.12) | 0.003 | — |
Note: OR: Odds Ratio; CI: confidence interval; *p Value for heterogeneity.