Table 1.
Selected characteristics of Iowa and Texas case mothers and control mothers in the National Birth Defects Prevention Study, 1997–2005 [n (%)].
| Characteristic | Controls (n=1,551) | Cases | |||
|---|---|---|---|---|---|
| NTDs (n=317) | Limb deficiencies (n=177) | Oral cleft defects (n=654) | Heart defects (n=2,011) | ||
| aAny smoking between date of conception and end of first trimester. bExposure during the first trimester of pregnancy. cTotal daily nitrite intake=5% (drinking water nitrate+dietary nitrate)+dietary nitrite. dUse during the first trimester of pregnancy. eReported primary drinking water source at the beginning of pregnancy. fWater module questions were added in 1999. | |||||
| Race/ethnicity | |||||
| Non-Hispanic white | 901 (58.2) | 165 (52.2) | 93 (52.5) | 393 (60.2) | 1,033 (51.5) |
| Non-Hispanic black | 27 (1.7) | 9 (2.9) | 5 (2.8) | 12 (1.8) | 60 (3.0) |
| Hispanic | 555 (35.9) | 132 (41.8) | 67 (37.9) | 218 (33.4) | 833 (41.5) |
| Asian/Pacific Islander | 21 (1.4) | 1 (0.3) | 2 (1.1) | 12 (1.8) | 19 (0.9) |
| All others | 44 (2.8) | 9 (2.8) | 10 (5.7) | 18 (2.8) | 62 (3.1) |
| Missing | 3 | 1 | 0 | 1 | 4 |
| Education (years) | |||||
| <12 | 286 (18.8) | 64 (20.3) | 27 (15.6) | 138 (21.3) | 408 (20.6) |
| 12 | 443 (29.2) | 87 (27.6) | 57 (33.0) | 192 (29.7) | 574 (29.0) |
| 13–15 | 436 (28.7) | 105 (33.3) | 57 (32.9) | 186 (28.7) | 606 (30.6) |
| > 15 | 353 (23.3) | 59 (18.7) | 32 (18.5) | 131 (20.2) | 390 (19.7) |
| Missing | 33 | 2 | 4 | 7 | 33 |
| Age at delivery (years) | |||||
| <18 | 95 (6.1) | 11 (3.5) | 7 (4.0) | 29 (4.4) | 98 (4.9) |
| 18–19 | 130 (8.4) | 29 (9.1) | 19 (10.7) | 61 (9.3) | 159 (7.9) |
| 20–24 | 380 (24.5) | 79 (24.9) | 48 (27.1) | 208 (31.8) | 535 (26.6) |
| 25–29 | 453 (29.2) | 100 (31.5) | 55 (31.1) | 170 (26.0) | 551 (27.4) |
| 30–34 | 344 (22.2) | 68 (21.5) | 35 (19.8) | 114 (17.4) | 446 (22.2) |
| > 34 | 149 (9.6) | 30 (9.5) | 13 (7.3) | 72 (11.0) | 222 (11.0) |
| Study center | |||||
| Iowa | 759 (48.9) | 146 (46.1) | 80 (45.2) | 306 (46.8) | 769 (38.2) |
| Texas | 792 (51.1) | 171 (53.9) | 97 (54.8) | 348 (53.2) | 1,242 (61.8) |
| Smokinga | |||||
| No | 1,199 (78.7) | 259 (82.2) | 132 (76.3) | 471 (72.6) | 1,548 (78.1) |
| Yes | 324 (21.3) | 56 (17.8) | 41 (23.7) | 178 (27.4) | 433 (21.9) |
| Missing/out of range | 28 | 2 | 4 | 5 | 30 |
| Nitrosatable drug exposureb | |||||
| No | 1,166 (77.6) | 216 (70.8) | 120 (71.9) | 482 (76.4) | 1,475 (76.2) |
| Yes | 336 (22.4) | 89 (29.2) | 47 (28.1) | 149 (23.6) | 460 (23.8) |
| Total daily nitrite intakec | |||||
| ≤ 4.78mg/day | 726 (66.1) | 145 (62.5) | 72 (55.8) | 334 (68.2) | 1,004 (63.5) |
| >4.78mg/day | 372 (33.9) | 87 (37.5) | 57 (44.2) | 156 (31.8) | 578 (36.5) |
| Multivitamin used | |||||
| No | 206 (13.6) | 33 (10.6) | 22 (12.9) | 100 (15.7) | 304 (15.5) |
| Yes | 1,308 (86.4) | 277 (89.4) | 148 (87.1) | 537 (84.3) | 1,658 (84.5) |
| Missing | 37 | 7 | 7 | 17 | 49 |
| Usual home source of drinking watere | |||||
| Tap water, municipal | 738 (58.3) | 173 (64.3) | 96 (64.0) | 354 (61.7) | 1,011 (56.3) |
| Tap water, private well | 72 (5.7) | 19 (7.1) | 14 (9.3) | 42 (7.3) | 99 (5.5) |
| Bottled water exclusively | 455 (36.0) | 77 (28.6) | 40 (26.7) | 178 (31.0) | 685 (38.2) |
| Not availablef | 286 | 48 | 27 | 80 | 216 |