Table 1.

Distribution of characteristics of interest by region.

Characteristic	Overall (n = 1,889)	Valencia (n = 608)	Sabadell (n = 471)	Asturias (n = 345)	Gipuzkoa (n = 465)
Mental development score	99.9 ± 15.2		100.7 ± 15.5		99.1 ± 14.6		101.6 ± 15.6		98.5 ± 15.2
Age at mental development assessment (months)	14.8 ± 2.6		12.4 ± 0.8		14.6 ± 0.7		19.4 ± 1.3		14.5 ± 0.8
NO2 exposure during pregnancy (μg/m3)	29.0 ± 11.2		36.8 ± 11.0		32.1 ± 8.8		23.2 ± 7.1		20.1 ± 6.5
Benzene exposure during pregnancy (μg/m3)	1.5 ± 0.9		2.2 ± 0.6		0.8 ± 0.3		2.3 ± 1.3		1.0 ± 0.3
Maternal fruit and vegetable consumption, first trimestera
Low tertile (≤ 405 g/day)	33.5		39.8		33.0		30.5		27.6
Medium/high tertile (> 405 g/day)	66.5		60.2		67.0		69.5		72.4
Breast-feeding duration
None	14.7		16.0		6.7		29.0		10.5
< 6 months	40.5		39.9		42.6		43.2		36.9
≥ 6 months	44.8		44.1		50.7		27.8		52.6
Maternal circulating vitamin D levelsb
Low	33.6		22.7		40.4		40.0		35.7
Medium	33.0		34.0		27.1		35.5		35.9
High	33.4		43.3		32.5		24.5		28.4
Parental social classc
I/II managers/technicians	32.8		23.5		32.0		32.6		45.8
III skilled manual/nonmanual	25.8		28.1		28.7		24.1		20.9
IV/V semiskilled/unskilled	41.4		48.4		29.3		43.3		33.3
Maternal education level
Primary or less	22.8		31.7		26.3		15.6		12.7
Secondary	41.2		43.3		42.5		43.2		35.7
University degree	36.0		25.0		31.2		41.2		51.6
Values are percentages for categorical variables and mean ± SD for continuous variables. aLow versus medium/high tertile of maternal fruit and vegetable consumption. bSeason-specific tertiles of maternal circulating vitamin D levels (see “Materials and Methods”). cSocial class data from Instituto Nacional de Estadística (1994).