Table 5.
Association Between Anencephaly or Spina Bifida and Dietary Folic Acid Intake Stratified by Supplement Use,a National Birth Defects Prevention Study, 1998–2003
| No. of Cases | No. of Controls | Crude |
Adjustedbc |
|||
| Odds Ratio | 95% Confidence Interval | Odds Ratio | 95% Confidence Interval | |||
| Anencephaly | ||||||
| No supplement use B3–P1 | ||||||
| ≤10th folic acid intake | 9 | 193 | 1.2 | 0.6, 2.6 | 1.2 | 0.6, 2.6 |
| 11th–30th folic acid intake | 19 | 332 | 1.5 | 0.9, 2.7 | 1.7 | 0.9, 3.0 |
| 31st–50th folic acid intake | 19 | 342 | 1.5 | 0.8, 2.6 | 1.5 | 0.8, 2.7 |
| >50th folic acid intake | 34 | 911 | Referent | Referent | Referent | Referent |
| Supplement users B3–P1 | ||||||
| ≤10th folic acid intake | 5 | 85 | 1.4 | 0.5, 4.0 | 1.5 | 0.5, 4.0 |
| 11th–30th folic acid intake | 6 | 208 | 0.7 | 0.3, 1.8 | 0.7 | 0.3, 1.8 |
| 31st–50th folic acid intake | 8 | 204 | 1.0 | 0.4, 2.2 | 1.0 | 0.4, 2.3 |
| >50th folic acid intake | 19 | 468 | Referent | Referent | Referent | Referent |
| Supplement users, P1 initiators | ||||||
| ≤10th folic acid intake | 7 | 92 | 1.7 | 0.7, 4.1 | 1.7 | 0.7, 4.2 |
| 11th–30th folic acid intake | 22 | 198 | 2.5 | 1.3, 4.6 | 2.5 | 1.4, 4.8 |
| 31st–50th folic acid intake | 11 | 193 | 1.3 | 0.6, 2.7 | 1.3 | 0.6, 2.8 |
| >50th folic acid intake | 21 | 465 | Referent | Referent | Referent | Referent |
| Spina bifida | ||||||
| No supplement use B3–P1 | ||||||
| ≤10th folic acid intake | 12 | 193 | 0.6 | 0.3, 1.1 | 0.5 | 0.3, 1.1 |
| 11th–30th folic acid intake | 53 | 332 | 1.5 | 1.0, 2.1 | 1.5 | 1.0, 2.2 |
| 31st–50th folic acid intake | 26 | 342 | 0.7 | 0.5, 1.1 | 0.7 | 0.4, 1.1 |
| >50th folic acid intake | 97 | 911 | Referent | Referent | Referent | Referent |
| Supplement users B3–B1 | ||||||
| ≤10th folic acid intake | 13 | 85 | 1.8 | 0.9, 3.6 | 1.8 | 0.9, 3.5 |
| 11th–30th folic acid intake | 29 | 208 | 1.7 | 1.0, 2.8 | 1.7 | 1.0, 2.8 |
| 31st–50th folic acid intake | 16 | 204 | 0.9 | 0.5, 1.7 | 0.9 | 0.5, 1.7 |
| >50th folic acid intake | 39 | 468 | Referent | Referent | Referent | Referent |
| Supplement users, P1 initiators | ||||||
| ≤10th folic acid intake | 7 | 92 | 0.6 | 0.3, 1.4 | 0.7 | 0.3, 1.5 |
| 11th–30th folic acid intake | 16 | 198 | 0.6 | 0.4, 1.2 | 0.7 | 0.4, 1.2 |
| 31st–50th folic acid intake | 19 | 193 | 0.8 | 0.5, 1.4 | 0.8 | 0.4, 1.4 |
| >50th folic acid intake | 58 | 465 | Referent | Referent | Referent | Referent |
Abbreviations: B3, 3 months before pregnancy; P1, first month of pregnancy.
a
Dietary folic acid supplement use stratifications by percentile.
b
Adjusted anencephaly models include maternal race and education.
c
Adjusted spina bifida models include maternal race, maternal body mass index, and pregnancy intent.