Table 1.
The maternal characteristics of case and control participants
| Variable | Cases (n = 322) | Controls (n = 333) | Z / χ2 | P value |
|---|---|---|---|---|
| Maternal age | ||||
| Median (interquartile range) | 27.00(6.00) | 28.00(6.00) | -2.13 | 0.033* |
| Maternal BMI | ||||
| Median (interquartile range) | 23.44(3.89) | 23.14 (4.41) | 0.39 | 0.679 |
| The number of weeks of folic acid taken after pregnancy | ||||
| Median (interquartile range) | 12.00(12.00) | 12.00(8.00) | -3.13 | 0.002* |
| Gestational age | ||||
| Median (interquartile range) | 26.00(6.93) | 24.86(4.86) | 2.46 | 0.014* |
| Maternal residence | ||||
| Urban | 190 (59.01) | 263(78.98) | 37.99 | < 0.001* |
| Suburbs | 88 (27.33) | 59 (17.72) | ||
| Rural | 41 (12.73) | 9 (2.70) | ||
| Outside exposure | ||||
| Yes | 96 (29.81) | 51 (15.32) | 19.77 | < 0.001* |
| No | 266 (70.19) | 282(84.68) | ||
| First pregnancy | ||||
| Yes | 129(40.06) | 160 (48.05) | 5.13 | 0.077 |
| No | 192 (59.63) | 173 (51.95) | ||
| City | ||||
| Fujian | 39(38.61) | 62(61.39) | 5.64 | 0.131 |
| Hubei | 58 (53.21) | 51 (46.79) | ||
| Henan | 64 (51.61) | 60 (48.39) | ||
| Shenzhen | 161 (50.16) | 160(49.84) | ||
Data are median (interquartile range) or numbers (%)
aObtained using the Mann–Whitney U test for maternal age, maternal BMI, the number of weeks of folic acid taken after pregnancy and gestational age; the χ2 test for maternal residence, outside exposure, first pregnancy, and city
*Significant results, P value < 0.05