Table 3.
Univariate analysis of research factors among cases and controls
| Research factors | Controls (N=327) | Cases (N=327) | χ2 value | P value | ||
|---|---|---|---|---|---|---|
| N | % | N | % | |||
| Permanent residence | 0.646 | 0.421 | ||||
| Rural area | 80 | 75.5 | 89 | 27.2 | ||
| Downtown | 247 | 24.5 | 238 | 72.8 | ||
| Ethnicity | 0.358 | 0.549 | ||||
| Han | 262 | 80.1 | 268 | 82.0 | ||
| Minorities | 65 | 19.9 | 59 | 18.0 | ||
| Education level* | 9.100 | 0.011 | ||||
| Primary school and below | 45 | 13.8 | 44 | 13.5 | ||
| Middle school | 76 | 23.2 | 110 | 33.6 | ||
| College and above | 206 | 63.0 | 173 | 52.9 | ||
| History of abnormal reproduction* | 8.203 | 0.004 | ||||
| None | 299 | 91.4 | 275 | 84.1 | ||
| Yes | 28 | 8.6 | 52 | 15.9 | ||
| Family history of congenital heart disease* | 4.098 | 0.043 | ||||
| None | 290 | 88.7 | 272 | 83.2 | ||
| Yes | 37 | 11.3 | 55 | 16.8 | ||
| BMI | 4.310 | 0.230 | ||||
| Thin (≤18.4) | 36a | 11.0 | 45a | 13.8 | ||
| Normal (18.5-23.9) | 192a | 58.7 | 171a | 52.3 | ||
| Overweight (24.0-27.9) | 90a | 27.5 | 95a | 29.1 | ||
| Obese (≥28.0) | 9a | 2.8 | 16a | 4.9 | ||
| Respiratory infections* | 10.910 | 0.001 | ||||
| None | 267 | 81.7 | 231 | 70.6 | ||
| Yes | 60 | 18.3 | 96 | 29.4 | ||
| Infection of female reproductive system* | 8.724 | 0.003 | ||||
| None | 318 | 97.2 | 301 | 92.0 | ||
| Yes | 9 | 2.8 | 26 | 8.0 | ||
| Medication history* | 8.402 | 0.004 | ||||
| None | 262 | 80.1 | 230 | 70.3 | ||
| Yes | 65 | 19.9 | 97 | 29.7 | ||
| Electrical radiation* | 7.618 | 0.022 | ||||
| None | 104 | 31.8 | 85 | 27.8 | ||
| Yes | 223 | 68.2 | 247 | 72.2 | ||
| Noise | 2.810 | 0.094 | ||||
| None | 300 | 91.7 | 287 | 87.8 | ||
| Yes | 27 | 8.3 | 40 | 12.2 | ||
| Heavy metals* | 6.146 | 0.013 | ||||
| None | 310 | 94.8 | 288 | 89.6 | ||
| Yes | 17 | 5.2 | 34 | 10.4 | ||
| Pesticides* | 7.181 | 0.007 | ||||
| None | 318 | 97.2 | 303 | 92.7 | ||
| Yes | 9 | 2.8 | 24 | 7.3 | ||
| Organic solvents | 2.353 | 0.125 | ||||
| None | 285 | 87.2 | 271 | 82.9 | ||
| Yes | 42 | 12.8 | 56 | 17.1 | ||
| Air pollution | 3.570 | 0.059 | ||||
| None | 274 | 83.8 | 255 | 78.0 | ||
| Yes | 53 | 16.2 | 72 | 22.0 | ||
| Water pollution* | 22.731 | 0.000 | ||||
| None | 305 | 93.3 | 264 | 80.7 | ||
| Yes | 22 | 6.7 | 63 | 19.3 | ||
| Active smoking* | 6.498 | 0.039 | ||||
| None | 294 | 89.9 | 278 | 85.0 | ||
| Yes | 33 | 10.1 | 49 | 15.0 | ||
| Passive smoking* | 11.779 | 0.001 | ||||
| None | 275 | 84.1 | 239 | 73.1 | ||
| Yes | 52 | 15.9 | 88 | 26.9 | ||
| Drinking* | 11.422 | 0.003 | ||||
| None | 300 | 91.7 | 272 | 83.2 | ||
| Yes | 27 | 8.3 | 55 | 16.8 | ||
| Addictive drugs | 0.914 | 0.339 | ||||
| None | 320 | 97.9 | 316 | 96.6 | ||
| Yes | 7 | 2.1 | 11 | 3.4 | ||
| Sleep disorder* | 4.407 | 0.036 | ||||
| None | 310 | 94.8 | 293 | 90.5 | ||
| Yes | 17 | 5.2 | 29 | 9.5 | ||
| Adverse emotions during pregnancy* | 56.652 | 0.000 | ||||
| None | 245 | 74.9 | 156 | 48.4 | ||
| Yes | 82 | 25.1 | 171 | 52.3 | ||
| Nutrition supplementation* | 14.371 | 0.000 | ||||
| None | 180 | 55.0 | 227 | 69.4 | ||
| Yes | 147 | 45.0 | 100 | 30.6 | ||
| Periodic prenatal examination* | 4.155 | 0.042 | ||||
| None | 139 | 42.5 | 165 | 50.5 | ||
| Yes | 188 | 57.5 | 162 | 49.5 | ||
Note: BMI: Body mass index;
*Statistically significant after univariate analysis with a test criterion of 0.05; Each subscript letter denoted a subset of categories whose column proportions do not differ significantly from each other at the 0.05 level.