Table 1. Demographic characteristics of the study cohort.
| Parity | P-value | ||||
| 1 (n = 157 207) |
2 (n = 564 727) |
3 (n = 436 250) |
4+ (n = 134 278) |
||
| Age at recruitment (first birth) | 26.37 ± 4.41 | 24.86 ± 3.30 | 23.49 ± 2.95 | 22.43 ± 2.93 | <0.0001 |
| Marital status | |||||
| Married | 146 022 (92.89) | 554 810 (98.24) | 429 239 (98.39) | 130 544 (97.22) | <0.0001 |
| Not married | 11 185 (7.11) | 9917 (1.76) | 7011 (1.61) | 3734 (2.78) | |
| Years of schooling | |||||
| ≤9 | 72 090 (45.86) | 258 361 (45.75) | 285 737 (65.50) | 106 330 (79.19) | <0.0001 |
| >9 | 85 117 (54.14) | 306 366 (54.25) | 150 513 (34.50) | 27 948 (20.81) | |
| Birthplace | |||||
| Hospital/clinic | 153 167 (97.43) | 553 930 (98.09) | 416 492 (98.47) | 122 336 (91.11) | <0.0001 |
| Home/other | 4040 (2.57) | 10 797 (1.91) | 19 758 (4.53) | 11 942 (8.89) | |