Table 1. Maternal characteristics for 616 case families and 1,645 control families enrolled in National Birth Defects Prevention Study between 1997 and 2008.
| Case | Control | |
| (N = 616) | (N = 1,645) | |
| Age at delivery (years) | 28.3±6.1 | 27.5±6.0 |
| Race | ||
| African American | 49 (8%) | 143 (9%) |
| Caucasian | 401 (66%) | 1,136 (69%) |
| Hispanic | 123 (20%) | 285 (17%) |
| Others | 39 (6%) | 78 (5%) |
| Missing information | 4 | 3 |
| Education | ||
| <12 years | 83 (14%) | 217 (13%) |
| High school degree or equivalent | 167 (27%) | 413 (25%) |
| 1–3 years of college | 173 (28%) | 454 (28%) |
| At least 4 years of college or Bachelor degree | 190 (31%) | 559 (34%) |
| Missing information | 3 | 2 |
| Household income | ||
| Less than 10 Thousand | 94 (16%) | 236 (15%) |
| 10 to 30 Thousand | 150 (26%) | 408 (27%) |
| 30 to 50 Thousand Dollars | 118 (20%) | 348 (23%) |
| More than 50 Thousand | 217 (37%) | 538 (35%) |
| Missing information | 37 | 115 |
| Folic acid supplements | ||
| No | 299 (49%) | 738 (45%) |
| Yes1 | 314 (51%) | 907 (55%) |
| Missing information | 3 | 0 |
| BMI | ||
| Underweight (BMI <18.5) | 31 (5%) | 74 (5%) |
| Normal weight (18.5< = BMI <25) | 298 (50%) | 880 (55%) |
| Overweight (25< = BMI <30) | 141 (24%) | 360 (23%) |
| Obese (> = 30) | 121 (20%) | 281 (18%) |
| Missing information | 25 | 50 |
| Alcohol consumption | ||
| No | 460 (76%) | 1,251 (76%) |
| Yes2 | 149 (24%) | 390 (24%) |
| Missing information | 7 | 4 |
| Tobacco use | ||
| No | 498 (81%) | 1,356 (82%) |
| Yes3 | 114 (19%) | 288 (18%) |
| Missing information | 4 | 1 |
Summary statistics were expressed as mean ± standard deviation for continuous variables, and frequency (percentage) for categorical variables.
1
Folic acid supplements yes is defined as maternal use of folic acid supplements at least two months during the exposure window (i.e. one month prior to conception and two months after conception).
2
Alcohol consumption yes is defined as drinking during the three months after pregnancy.
3
Tobacco use yes is defined as cigarette smoking during the three months after pregnancy.