Variable | Control, n = 490 (%) | Cases, n= 399 (%) | Chi square | P value |
---|---|---|---|---|
Maternal age (years, n) a | Â | Â | 7.803 | 0.099 |
n < 20 | 12 (2.4) | 12 (3.0) | Â | Â |
 20 ≤ n < 25 | 111 (22.7) | 113 (28.3) |  |  |
 25 ≤ n < 30 | 216 (44.1) | 179 (44.9) |  |  |
 30 ≤ n< 35 | 108 (22.0) | 73 (18.3) |  |  |
n ≥ 35 | 43 (8.8) | 22 (5.5) |  |  |
Gestational age (week, n) a | Â | Â | 37.628 | < 0.001*** |
n < 15 | 6 (1.2) | 2 (0.5) | Â | Â |
 15 ≤ n< 20 | 69 (14.1) | 15 (3.8) |  |  |
 20 ≤ n < 25 | 233 (47.6) | 182 (45.6) |  |  |
 26 ≤ n<31 | 109 (22.2) | 136 (34.1) |  |  |
n ≥ 31 | 73 (14.9) | 64 (16.0) |  |  |
Folic acid supplement | Â | Â | 11.350 | 0.001** |
 Yes | 436 (89.0) | 323 (81.0) |  |  |
 No | 54 (11.0) | 76 (19.0) |  |  |
Parental smoking | Â | Â | 15.615 | < 0.001*** |
 Yes | 181 (36.9) | 200 (50.1) |  |  |
 No | 309 (63.1) | 199 (49.9) |  |  |
ppBMI (kg/cm2) | Â | Â | 3.987 | 0.136 |
 BMI < 18.5 | 120 (23.1) | 116 (27.6) |  |  |
 18.5 ≤ BMI< 25 | 381 (73.3) | 295 (70.2) |  |  |
 BMI ≥ 25 | 19 (3.7) | 9 (2.1) |  |  |
mEDU | Â | Â | 38.113 | < 0.001*** |
 Primary school and below | 3 (0.6) | 16 (4.0) |  |  |
 Junior middle school | 77 (15.7) | 114 (28.6) |  |  |
 Senior high school | 124 (25.3) | 89 (22.3) |  |  |
 College degree and above | 284 (58.0) | 173 (43.4) |  |  |