Table 5.
Association Between Exposure to Nitrosatable Drugs Around the Time of Conceptiona and Neural Tube Defects, by Vitamin C Supplementation Level, National Birth Defects Prevention Study, 1997–2005
| Type of Neural Tube Defect, Vitamin C Supplementation Level c, and Type of Drug Exposure | Cases | Controls | Unadjusted ORd | 95% CI | Adjusted ORe | 95% CI | ||
| No. | % | No. | % | |||||
| Anencephalyb | ||||||||
| None | ||||||||
| No nitrosatable drug exposure | 147 | 86.0 | 2,804 | 86.7 | 1 | Referent | 1 | Referent |
| Secondary amines | 16 | 9.8 | 255 | 8.3 | 1.20 | 0.70, 2.04 | 1.44 | 0.84, 2.49 |
| Tertiary amines | 18 | 10.9 | 211 | 7.0 | 1.63 | 0.98, 2.71 | 2.11 | 1.25, 3.57 |
| Less than daily | ||||||||
| No nitrosatable drug exposure | 48 | 65.8 | 958 | 81.4 | 1 | Referent | 1 | Referent |
| Secondary amines | 13 | 21.3 | 123 | 11.4 | 2.11 | 1.11, 4.00 | 2.21 | 1.15, 4.23 |
| Tertiary amines | 15 | 23.8 | 117 | 10.9 | 2.56 | 1.39, 4.71 | 2.77 | 1.48, 5.17 |
| Daily | ||||||||
| No nitrosatable drug exposure | 77 | 77.0 | 1,785 | 79.1 | 1 | Referent | 1 | Referent |
| Secondary amines | 10 | 11.5 | 275 | 13.4 | 0.84 | 0.43, 1.65 | 0.91 | 0.46, 1.78 |
| Tertiary amines | 15 | 16.3 | 248 | 12.2 | 1.40 | 0.79, 2.48 | 1.52 | 0.86, 2.71 |
| Spina bifida | ||||||||
| None | ||||||||
| No nitrosatable drug exposure | 308 | 85.1 | 2,804 | 86.7 | 1 | Referent | 1 | Referent |
| Secondary amines | 31 | 9.1 | 255 | 8.3 | 1.11 | 0.75, 1.64 | 1.19 | 0.80, 1.77 |
| Tertiary amines | 35 | 10.2 | 211 | 7.0 | 1.51 | 1.04, 2.20 | 1.69 | 1.15, 2.48 |
| Less than daily | ||||||||
| No nitrosatable drug exposure | 108 | 81.8 | 958 | 81.4 | 1 | Referent | 1 | Referent |
| Secondary amines | 9 | 7.7 | 123 | 11.4 | 0.65 | 0.32, 1.31 | 0.68 | 0.34, 1.40 |
| Tertiary amines | 15 | 12.2 | 117 | 10.9 | 1.14 | 0.64, 2.02 | 1.25 | 0.70, 2.25 |
| Daily | ||||||||
| No nitrosatable drug exposure | 169 | 74.8 | 1,785 | 79.1 | 1 | Referent | 1 | Referent |
| Secondary amines | 31 | 15.5 | 275 | 13.4 | 1.19 | 0.80, 1.78 | 1.17 | 0.78, 1.76 |
| Tertiary amines | 34 | 16.8 | 248 | 12.2 | 1.45 | 0.98, 2.14 | 1.44 | 0.97, 2.13 |
Abbreviations: CI, confidence interval; OR, odds ratio.
a
The period from 1 month before conception to 1 month after conception.
b
This category included craniorachischisis.
c
Supplement taken the first month after conception (including prenatal multivitamin supplements, nonprenatal multivitamin supplements, and other vitamin C-containing supplements).
d
Crude and adjusted odds ratios included only cases and controls for whom we had complete information on drug exposures and covariates.
e
Adjusted for maternal race/ethnicity and educational level.