Table 1.
Maternal Characteristics among Neural Tube Defect Cases and Controls in the National Birth Defects Prevention Study, 1997–2004
| Cases (%), n = 1041 | Controls (%), n = 5862 | |
|---|---|---|
| Race-ethnicity1 | ||
| Non-Hispanic white | 544 (52.3) | 3527 (60.2) |
| Non-Hispanic black | 100 (9.6) | 669 (11.4) |
| Hispanic | 334 (32.1) | 1322 (22.6) |
| Asian/Pacific Islanders | 18 (1.7) | 174 (3.0) |
| Others | 45 (4.3) | 170 (2.9) |
| Age at conception (years)1 | ||
| <20 | 154 (14.8) | 823 (14.0) |
| 20–24 | 230 (22.1) | 1365 (23.3) |
| 25–29 | 331 (31.8) | 1571 (26.8) |
| 30–34 | 203 (19.5) | 1435 (24.5) |
| >35 | 123 (11.8) | 668 (11.4) |
| Education (years)1,2 | ||
| <12 | 221 (21.2) | 989 (16.9) |
| 12 | 305 (29.3) | 1462 (24.9) |
| >12 | 513 (49.3) | 3396 (57.9) |
| Body mass index1,3 | ||
| Normal or underweight | 546 (55.4) | 3480 (61.8) |
| Overweight | 216 (21.9) | 1254 (22.3) |
| Obese | 224 (22.7) | 897 (15.9) |
| Smoked cigarettes4 | ||
| Yes | 172 (16.5) | 1108 (18.9) |
| No | 869 (83.5) | 4754 (81.1) |
| Tobacco exposure1 | ||
| Smoked5 | 172 (16.5) | 1108 (18.9) |
| Passive smoke only | 218 (20.9) | 814 (13.9) |
| Not exposed6 | 651 (62.5) | 3940 (67.2) |
| Study Center1 | ||
| Arkansas | 137 (13.2) | 711 (12.1) |
| California | 213 (20.5) | 789 (13.5) |
| Georgia | 122 (11.7) | 620 (10.6) |
| Iowa | 130 (12.5) | 659 (11.2) |
| Massachusetts | 64 (6.2) | 743 (12.7) |
| North Carolina | 47 (4.5) | 286 (4.9) |
| New Jersey | 70 (6.7) | 576 (9.8) |
| New York | 62 (6.0) | 527 (9.0) |
| Texas | 149 (14.3) | 693 (11.8) |
| Utah | 47 (4.5) | 258 (4.4) |
1
Statistically significant differences in distribution between cases and controls at p < 0.05.
2
Two case mothers and 15 control mothers had missing values for education.
3
Fifty-five case women and 231 control women had missing values for body mass index.
4
During 1 month before or after conception.
5
Whether or not exposed to passive smoke.
6
Nonsmokers who were not exposed to passive smoke.