Table 1.
Characteristics of Mothers of Infants With Neural Tube Defects and of Infants without Birth Defects in the National Birth Defects Prevention Study, United States, 1997–2002
| Controls (N = 4143) | NTD (N = 768) | Spina bifida (N = 459) | Anencephaly (N = 218) | Encephalocele (N = 91) | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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| N | (%)a | N | (%)a | Pb | N | (%)a | Pb | N | (%)a | Pb | N | (%)a | Pb | |
| Age at conception (years) | 0.01 | 0.02 | 0.61 | 0.46 | ||||||||||
| 12–19 | 604 | (14.6) | 122 | (15.9) | 69 | (15.0) | 38 | (17.4) | 15 | (16.5) | ||||
| 20–29 | 2030 | (49.0) | 404 | (52.6) | 249 | (54.2) | 107 | (49.1) | 48 | (52.7) | ||||
| 30–34 | 1031 | (24.9) | 149 | (19.4) | 85 | (18.5) | 48 | (22.0) | 16 | (17.6) | ||||
| 35 or older | 478 | (11.5) | 93 | (12.1) | 56 | (12.2) | 25 | (11.5) | 12 | (13.2) | ||||
| Race/Ethnicity | <0.01 | <0.01 | <0.01 | 0.01 | ||||||||||
| Non-Hispanic white | 2477 | (59.9) | 399 | (52.0 | 252 | (55.0) | 107 | (49.1) | 40 | (44.0) | ||||
| Non-Hispanic black | 498 | (12.1) | 79 | (10.3) | 44 | (9.6) | 22 | (10.1) | 13 | (14.3) | ||||
| Hispanic | 940 | (22.7) | 251 | (32.7) | 142 | (31.0) | 76 | (34.9) | 33 | (36.3) | ||||
| Other | 217 | (5.3) | 38 | (5.0) | 20 | (4.4) | 13 | (6.0) | 5 | (5.5) | ||||
| Birthplace | 0.02 | 0.05 | 0.41 | 0.67 | ||||||||||
| United States | 3346 | (81.5) | 591 | (77.5) | 352 | (77.0) | 168 | (78.1) | 71 | (78.0) | ||||
| Other | 758 | (18.5) | 172 | (22.6) | 105 | (23.0) | 47 | (21.9) | 20 | (22.0) | ||||
| Education | <0.01 | <0.01 | <0.01 | 0.01 | ||||||||||
| <High school graduate | 679 | (16.6) | 167 | (22.1) | 92 | (20.1) | 54 | (25.1) | 21 | (23.1) | ||||
| High school graduate | 1032 | (25.2) | 230 | (30.0) | 136 | (29.8) | 63 | (29.3) | 31 | (34.1) | ||||
| College | 2390 | (58.3) | 366 | (47.9) | 229 | (50.1) | 98 | (45.6) | 39 | (42.9) | ||||
| Household income | <0.01 | <0.01 | 0.09 | 0.07 | ||||||||||
| ≤$50,000 | 2334 | (64.5) | 513 | (74.7) | 315 | (76.8) | 138 | (70.4) | 60 | (74.1) | ||||
| >$50,000 | 1284 | (35.5) | 174 | (25.3) | 95 | (23.2) | 58 | (29.6) | 21 | (25.9) | ||||
| Prepregnancy obesity | <0.01 | <0.01 | 0.52 | 0.06 | ||||||||||
| BMI <30 kg/m2 | 3386 | (85.2) | 553 | (76.1) | 313 | (72.1) | 173 | (83.6) | 67 | (77.9) | ||||
| BMI ≥30 kg/m2 | 587 | (14.8) | 174 | (23.9) | 121 | (27.9) | 34 | (16.4) | 19 | (22.1) | ||||
| Cigarette smokingc | 0.29 | 0.80 | 0.09 | 0.22 | ||||||||||
| No | 3315 | (80.5) | 627 | (82.2) | 365 | (80.0) | 184 | (85.2) | 78 | (85.7) | ||||
| Yes | 801 | (19.5) | 136 | (17.8) | 91 | (20.0) | 32 | (14.8) | 13 | (14.3) | ||||
| Alcohol consumptionc | <0.01 | 0.06 | 0.03 | 0.03 | ||||||||||
| No | 2497 | (60.9) | 511 | (67.1) | 298 | (65.5) | 148 | (68.5) | 65 | (72.2) | ||||
| Yes | 1602 | (39.1) | 250 | (32.9) | 157 | (34.5) | 68 | (31.5) | 25 | (27.8) | ||||
| Intake of folic acid-containing supplementd | 0.75 | 0.41 | 0.74 | 0.59 | ||||||||||
| No | 1934 | (47.8) | 360 | (48.5) | 220 | (49.9) | 98 | (46.7) | 40 | (44.9) | ||||
| Yes | 2110 | (52.2) | 383 | (51.5) | 221 | (50.1) | 112 | (53.3) | 49 | (55.1) | ||||
| Parity | 0.01 | 0.02 | 0.07 | 0.45 | ||||||||||
| 0 | 1655 | (40.0) | 271 | (35.3) | 157 | (34.3) | 74 | (33.9) | 40 | (44.0) | ||||
| ≥1 | 2479 | (60.0) | 496 | (64.7) | 301 | (65.7) | 144 | (66.1) | 51 | (56.0) | ||||
a
Numbers of cases and controls may vary due to missing or incomplete data. Percentages may not sum to 100 due to rounding.
b
P values derived from chi-squared tests.
c
Any, one month before through the third month of pregnancy.
d
Any, three months before through the first month of pregnancy.
BMI, body mass index; NTD, neural tube defects.