| Subgroups | Model 1 |  | Model 2 a |  | P for interaction |
---|---|---|---|---|---|---|
Crude OR (95%CI), P value | Â | Adjusted OR (95%CI), P value | Â | |||
Maternal age | < 30 years | 1.55 (1.17, 2.06), 0.003 |  | 1.66 (1.19, 2.33), 0.003 |  | 0.850 |
 | ≥ 30 years | 1.36 (0.89, 2.07), 0.150 |  | 2.04 (1.23, 3.36), 0.005 |  |  |
Education | High middle school and below | 1.11 (0.72, 1.72), 0.639 | Â | 1.61 (0.95, 2.72), 0.076 | Â | 0.375 |
 | Above high middle school | 1.85 (1.39, 2.46), < 0.001 |  | 2.01 (1.46, 2.76), < 0.001 |  |  |
Residence | Rural | 1.83 (1.30, 2.59), < 0.001 |  | 2.01 (1.38, 2.92), < 0.001 |  | 0.598 |
 | Urban | 1.49 (1.04, 2.13), 0.029 |  | 1.76 (1.17, 2.64), 0.006 |  |  |
Family wealth index | Â | Â | Â | Â | Â | Â |
 | Low | 1.07 (0.72, 1.57), 0.747 |  | 1.51 (0.94, 2.44), 0.088 |  | 0.074 |
 | Medium | 1.86 (1.23, 2.82), 0.003 |  | 2.19 (1.39, 3.44), < 0.001 |  |  |
 | High | 1.99 (1.25, 3.16), 0.004 |  | 2.27 (1.38, 3.75), 0.001 |  |  |
Parity | Â | Â | Â | Â | Â | Â |
 | 0 | 1.91 (1.47, 2.50), < 0.001 |  | 1.89 (1.41, 2.54), < 0.001 |  | 0.479 |
 | ≥ 1 | 1.36 (0.75, 2.49), 0.314 |  | 1.62 (0.81, 3.26), 0.176 |  |  |
Abortion history | Â | Â | Â | Â | Â | Â |
 | Yes | 1.88 (1.25, 2.83), 0.002 |  | 2.16 (1.40, 3.45), 0.001 |  | 0.204 |
 | No | 1.30 (0.97, 1.73), 0.077 |  | 1.68 (1.20, 2.35), 0.001 |  |  |