Table 1.
Distribution of socio-demographic characteristics between NTD cases and controls, NBDPS, 1997–2007
| Maternal characteristics | Cases (N=326) | Controls (N=1,781) | χ2* | ||
|---|---|---|---|---|---|
| N | % | N | % | ||
| Maternal age | |||||
| ≤19 years | 45 | 13.80 | 214 | 12.02 | 0.22 |
| 20–34 years | 231 | 70.86 | 1,342 | 75.35 | |
| ≥35 years | 50 | 15.34 | 225 | 12.63 | |
| Maternal race | |||||
| White non-Hispanic | 172 | 52.76 | 989 | 55.53 | 0.05 |
| Black non-Hispanic | 29 | 8.90 | 229 | 12.86 | |
| Hispanic | 101 | 30.98 | 448 | 25.15 | |
| Other/Mixed | 24 | 7.36 | 114 | 6.40 | |
| Maternal education | |||||
| <12 years | 168 | 51.53 | 752 | 42.22 | 0.0023 |
| ≥12 years | 155 | 47.55 | 1,003 | 56.32 | |
| Parity | |||||
| 0 | 108 | 33.13 | 678 | 38.07 | 0.18 |
| 1 | 114 | 34.97 | 606 | 34.03 | |
| ≥2 | 104 | 31.90 | 497 | 27.91 | |
| Prenatal care | |||||
| Yes | 320 | 98.16 | 1,759 | 98.76 | 0.28 |
| No | 6 | 1.84 | 20 | 1.12 | |
| Folic acid use first month | |||||
| Yes | 160 | 49.08 | 852 | 47.84 | 0.68 |
| No | 166 | 50.92 | 929 | 52.16 | |
| Body mass index | |||||
| Underweight (BMI < 18.5) | 16 | 4.91 | 87 | 4.88 | 0.11 |
| Normal (18.5 ≤ BMI < 25) | 146 | 44.79 | 923 | 51.82 | |
| Overweight (25 ≤ BMI < 30) | 77 | 23.62 | 382 | 21.45 | |
| Obese (BMI> 30) | 70 | 21.47 | 307 | 17.24 | |
| Fever first trimester | |||||
| Yes | 34 | 10.43 | 107 | 6.01 | 0.003 |
| No | 292 | 89.57 | 1,674 | 93.99 | |
| Family history of NTDs** | |||||
| Yes | 4 | 1.23 | 7 | 0.39 | 0.05 |
| No | 322 | 98.77 | 1,774 | 99.61 | |
| Diuretics/laxatives first trimester | |||||
| Yes | 31 | 9.51 | 232 | 13.03 | 0.08 |
| No | 295 | 90.49 | 1,547 | 86.86 | |
| Caffeine first trimester | |||||
| >100 mg | 141 | 43.25 | 736 | 41.33 | 0.52 |
| ≤100 mg | 185 | 56.75 | 1,045 | 58.67 | |
| Alcohol consumption first trimester | |||||
| Yes | 112 | 34.36 | 572 | 32.12 | 0.49 |
| No | 212 | 65.03 | 1,182 | 66.37 | |
| Maternal smoking first trimester | |||||
| Yes | 65 | 19.94 | 303 | 17.01 | 0.21 |
| No | 259 | 79.45 | 1,460 | 81.98 | |
| Secondhand smoke first trimester | |||||
| Yes | 90 | 27.61 | 421 | 23.64 | 0.12 |
| No | 232 | 71.17 | 1,338 | 75.13 | |
| Climate region | |||||
| South (AR, TX) | 76 | 23.31 | 458 | 25.72 | 0.002 |
| Southeast (NC, GA) | 65 | 19.94 | 394 | 22.12 | |
| Northeast (NY) | 23 | 7.06 | 213 | 11.96 | |
| Southwest (UT) | 31 | 9.51 | 168 | 9.43 | |
| West (CA) | 80 | 24.54 | 282 | 15.83 | |
| Upper Midwest (IA) | 51 | 15.64 | 266 | 14.94 | |
| Imputed maternal residence dates | 0.08 | ||||
| Yes | 64 | 19.63 | 281 | 15.78 | |
| No | 262 | 80.37 | 1,500 | 84.22 | |
*
Chi‐square test of equal proportions;
**
Fisher’s exact test; the total percentage may not add to 100 because the counts on variables with missing values are not shown.
NTD = neural tube defects; NBDPS = National Birth Defects Prevention Study; BMI = body mass index; AR = Arkansas; TX = Texas; NC = North Carolina; GA = Georgia; NY = New York; UT = Utah; CA = California; IA = Iowa