Table 1.

Characteristics of subjects, San Joaquin Valley of California, 1997–2006.

	Percent of casesa (n = 569)	Percent of controlsa (n = 785)
Maternal race/ethnicity
White	31	33
U.S.-born Hispanic	22	25
Foreign-born Hispanic	33	28
Other	14	14
Maternal age at delivery   (years)
<20	12	17
20–24	25	28
25–29	31	26
30–34	20	18
>35	11	10
Maternal education (years)
< 12	33	30
12	29	28
> 12	37	41
Parity
0	33	37
1	30	31
2+	37	32
Prepregnancy BMI (kg/m2)
Underweight BMI ( < 18.5)	5	5
Normal weight   (18.5 ≤ BMI < 25)	44	47
Overweight    (25 ≤ BMI < 30)	23	24
Obese ( ≥ 30)	22	18
Multi-vitamin Useb
Yes	64	64
No	35	34
Smokingb
None	86	85
Any	14	15
Drinkingb
None	73	69
Any	27	31
Plurality
Singletons	95	99

^aPercentages may not equal 100 owing to rounding or missing data.

^bDuring the month before or the first two months of pregnancy.