Table 4.
Basic characteristics of cases and controls in the total datasets and in mothers who used folic acid in the first month of pregnancy, i.e. preconceptionally
| Cases | Controls | |||||||
|---|---|---|---|---|---|---|---|---|
| Totaldataset(N=22,843) | Folic acid use in thefirst month(N=684) | Totaldataset(N=38,151) | Folic acid use in thefirst month(N=1,526) | |||||
| N | % | N | % | N | % | N | % | |
| Maternal age (yr) | ||||||||
| < 25 | 10,945 | 47.9 | 327 | 47.8 | 17,994 | 47.2 | 746 | 48.9 |
| 25 – 29 | 7,154 | 31.3 | 236 | 34.5 | 12,885 | 33.8 | 513 | 33.6 |
| > 29 | 4,744 | 20.8 | 121 | 17.7 | 7,272 | 19.1 | 267 | 17.5 |
| Mean (± S.D.) | 25.4 (5.3) | 25.2 (4.9) | 25.4 (4.9) | 25.3 (4.8) | ||||
| Birth order | ||||||||
| 1 | 1,299 | 62.3 | 429 | 62.7 | 24,184 | 63.4 | 949 | 62.2 |
| ≥ 2 | 8,614 | 37.7 | 255 | 37.3 | 13,967 | 36.6 | 577 | 37.8 |
| Mean (± S.D.) | 1.9 (1.1) | 1.8 (1.1) | 1.7 (0.9) | 1.7 (0.9) | ||||
| Unmarried | 1,040 | 4.5 | 28 | 4.1 | 1,217 | 3.2 | 34 | 2.2 |
| Employment status | ||||||||
| Professional | 1,091 | 8.3 | 74 | 10.8 | 4,353 | 11.4 | 202 | 13.2 |
| Managerial | 4,968 | 21.7 | 191 | 27.9 | 10,134 | 26.6 | 479 | 31.4 |
| Skilled worker | 6,329 | 27.7 | 199 | 29.1 | 11,690 | 30.6 | 429 | 28.1 |
| Semiskilled worker | 3,869 | 16.9 | 106 | 15.5 | 5,783 | 15.2 | 203 | 13.3 |
| Unskilled worker | 1,503 | 6.6 | 34 | 5.0 | 1,859 | 4.9 | 61 | 4.0 |
| Housewife | 2,128 | 9.3 | 36 | 5.3 | 2,038 | 5.3 | 58 | 3.8 |
| Others | 2,145 | 9.4 | 44 | 6.4 | 2,294 | 6.0 | 94 | 6.2 |
| Pregnancy supplements | ||||||||
| Multivitamins in the first gestational month | 1,330 | 5.8 | 45 | 3.4 | 2,509 | 6.9 | 110 | 4.4 |