Table 1 General life indicators and pregnancy history of the female participants
| Â | Jiangsu (n = 1011) | Hebei (n = 1795) | Comparison | ||
|---|---|---|---|---|---|
| Â | N (%) or median (IQR) | Â | |||
Age, y | 28.3 (IQR = 4) | 27.3 (IQR = 6) | P <0.001 (Rank Sum) | ||
 15–18 | 0 | — | 1 | (0.1%) | |
 18–25 | 239 | (23.6%) | 673 | (37.5%) |  |
 26–35 | 733 | (72.5%) | 1007 | (56.1%) |  |
 36–45 | 39 | (3.9%) | 112 | (6.2%) |  |
 45+ | 0 | — | 2 | (0.1%) |  |
Occupation |  |  |  |  | χ2 = 901.78, P < 0.001 |
 Unemployed | 266 | (26.3%) | 1140 | (63.5%) | |
 IT | 2 | (0.2%) | 10 | (0.6%) |  |
 Sales | 43 | (4.3%) | 30 | (1.7%) |  |
 Office | 386 | (38.2%) | 65 | (3.6%) |  |
 Service | 94 | (9.3%) | 210 | (11.7%) |  |
 Labor | 87 | (8.6%) | 125 | (7.0%) |  |
 Medical | 34 | (3.4%) | 9 | (0.5%) |  |
 Teaching | 93 | (9.2%) | 34 | (1.9%) |  |
 Student | 2 | (0.2%) | 0 | — |  |
 Legal | 4 | (0.4%) | 0 | — |  |
 Peasant | 0 |  | 172 | (9.6%) |  |
Education |  |  |  |  | χ2 = 916.33, P < 0.001 |
 Illiteracy | 10 | (1.0%) | 4 | (0.2%) | |
 Below Primary | 7 | (0.7%) | 8 | (0.4%) |  |
 Primary | 29 | (2.9%) | 74 | (4.1%) |  |
 High school | 318 | (31.5%) | 1522 | (84.8%) |  |
 University & above | 647 | (64.0%) | 187 | (10.4%) |  |
Place of living |  |  |  |  | χ2 = 1583.2, P < 0.001 |
 Urban | 806 | (79.7%) | 113 | (6.7%) | |
 Rural | 205 | (20.3%) | 1682 | (93.7%) |  |
Number of people living with |  |  |  | χ2 = 110.46, P < 0.001 | |
 1 | 469 | (46.3%) | 659 | (36.7%) | |
 2 | 166 | (16.4%) | 275 | (15.3%) |  |
 3 | 257 | (25.4%) | 346 | (19.3%) |  |
 4 | 93 | (9.2%) | 433 | (24.1%) |  |
 5 and more | 26 | (2.6%) | 82 | (4.5%) |  |
Number of rooms per person in the house/apartment | χ2 = 23.17, P < 0.001 | ||||
 1 and less | 201 | (19.9%) | 425 | (23.7%) | |
 2 | 615 | (60.8%) | 1140 | (63.5%) |  |
 3 and more | 195 | (19.3%) | 229 | (12.8%) |  |
Previous pregnancy | Â | Â | Â | Â | Â |
 History of pregnancy | 435 | (43.0%) | 1004 | (55.9%) | χ2 = 16.19, P = 0.001 |
History of Abortion | 287 | (28.4%) | 273 | (15.2%) | χ2 = 70.32, P < 0.001 |
History of miscarriage | 132 | (13.1%) | 87 | (4.8%) | χ2 = 4.3, P = 0.038 |
History of stillbirth | 8 | (1.8%) | 28 | (10.3%) | χ2 = 3.02, P = 0.082 |
History of successful delivery | 126 | (29.0%) | 826 | (82.3%) | χ2 = 324.82, P < 0.001 |
Infants produced | 128 | Â | 829 | Â | Â |
 Premature | 9 | (7.0%) | 17 | (2.1%) | P < 0.004 (Two-tailed) |
 Low birth weight | 5 | (3.9%) | 15 | (1.8%) | P = 0.171 (Two-tailed) |
 Birth defects | 14 | (10.9%) | 16 | (1.9%) | P < 0.001 (Two-tailed) |