Table 2

Distribution of selected child and maternal characteristics and exposures for analysis of non-NTDs, NBDPS, 1997–2011

Characteristic or exposureIndividuals, No. (%)*
Controls
(n = 10 671)
All non-NTDs
(n = 15 110)
Child characteristic
Sex
 Male5443 (51.1)9704 (64.3)
 Female5217 (48.9)5390 (35.7)
 Missing1116
First-degree family history of same defect
 Yes--†--†
 No----
 Missing00
Study site
 Arkansas1318 (12.4)1966 (13.0)
 California1162 (10.9)1861 (12.3)
 Georgia1131 (10.6)1574 (10.4)
 Iowa1178 (11.0)1472 (9.7)
 Massachusetts1268 (11.9)2045 (13.5)
 New Jersey517 (4.8)828 (5.5)
 New York892 (8.4)1131 (7.5)
 North Carolina916 (8.6)1169 (7.7)
 Texas1264 (11.8)1305 (8.6)
 Utah1025 (9.6)1759 (11.6)
 Missing00
Maternal characteristic
Race/ethnicity
 Non-Hispanic white6127 (57.5)9437 (62.5)
 Non-Hispanic black1169 (11.0)1267 (8.4)
 Hispanic2672 (25.1)3385 (22.4)
 Other696 (6.5)1019 (6.7)
 Missing72
Age at delivery (years)
 <253532 (33.1)5199 (34.4)
 25–345666 (53.1)7737 (51.2)
 ≥351473 (13.8)2174 (14.4)
 Missing00
Educational level at delivery (years)
 <121765 (17.0)2427 (16.5)
 12–155211 (50.3)7716 (52.5)
 ≥163381 (32.6)4558 (31.0)
 Missing314409
Prepregnancy BMI (kg/m2)
 <18.5558 (5.5)819 (5.7)
 18.5–24.95487 (54.0)7719 (53.4)
 25.0–29.92306 (22.7)3302 (22.9)
 ≥30.01810 (17.8)2607 (18.0)
 Missing510663
Maternal exposure
Hypertension‡
 Yes944 (8.9)1676 (11.2)
 No9640 (91.1)13 328 (88.8)
 Missing87106
Cigarette smoking§
 No active or passive7253 (70.0)9740 (66.2)
 Active only783 (7.6)1225 (8.3)
 Passive only1292 (12.5)1968 (13.4)
 Active and passive1039 (10.0)1779 (12.1)
 Missing304398
Alcohol consumption§
 Yes3818 (36.8)5549 (37.7)
 No6546 (63.2)9155 (62.3)
 Missing307406
Fever§
 Yes1054 (10.7)1602 (11.7)
 No8803 (89.3)12 063 (88.3)
 Missing8141445
Use of a supplement containing folic acid§
 Yes9100 (87.5)12 975 (87.9)
 No1296 (12.5)1783 (12.1)
 Missing275352
  • *Percentages within each column may not total 100 due to rounding.

  • †See online supplemental Tables 4–9 for frequencies for each defect.

  • ‡Diagnosed before or during pregnancy.

  • §One month before pregnancy through the third month of pregnancy.

  • BMI, body mass index; NBDPS, National Birth Defects Prevention Study; NTDs, neural tube defects.