Table 1 Baseline characteristics in the case and control groups.
Baseline characteristics | Control(n = 504) | CHDs (n = 464) | t/χ2 | P | ||
|---|---|---|---|---|---|---|
N | % | N | % | |||
Gestational age (years) | 28.56 ± 4.70 | 27.77 ± 5.40 | 2.399 | 0.016 | ||
Education level | 12.306 | < 0.001 | ||||
Less than primary | 6 | 1.2 | 66 | 14.2 | ||
Junior high school | 100 | 19.8 | 190 | 40.9 | ||
Senior middle school | 168 | 33.3 | 130 | 28.1 | ||
College or higher | 230 | 45.7 | 78 | 16.8 | ||
Average annual income (RMB) | 15.946 | < 0.001 | ||||
≤ 50,000 | 144 | 28.6 | 372 | 80.2 | ||
60,000–100,000 | 216 | 42.9 | 68 | 14.7 | ||
110,000–150,000 | 46 | 9.1 | 10 | 2.1 | ||
≥ 160,000 | 98 | 19.4 | 14 | 3.0 | ||
Body mass index | 2.446 | 0.294 | ||||
< 18.5 | 126 | 25.0 | 98 | 21.2 | ||
18.5–23.99 | 288 | 57.1 | 286 | 61.6 | ||
≥ 24 | 90 | 17.9 | 80 | 17.2 | ||
History of diabetes | 28.414 | < 0.001 | ||||
No | 482 | 95.6 | 398 | 85.8 | ||
Yes | 22 | 4.4 | 66 | 14.2 | ||
Smoking history | 14.046 | < 0.001 | ||||
No | 494 | 98.0 | 432 | 93.1 | ||
Yes | 10 | 2.0 | 32 | 6.9 | ||
Second-hand smoke exposure history | 21.589 | < 0.001 | ||||
No | 316 | 62.7 | 222 | 47.8 | ||
Yes | 188 | 37.3 | 242 | 52.2 | ||
History of drinking alcohol | 9.060 | 0.003 | ||||
No | 468 | 92.9 | 404 | 87.1 | ||
Yes | 36 | 7.1 | 60 | 12.9 | ||
Folic acid supplement | 23.917 | < 0.001 | ||||
No | 34 | 6.7 | 78 | 16.8 | ||
Yes | 470 | 93.3 | 386 | 83.2 | ||
