Table 1.

Characteristics of the mothers included and those excluded because of missing data*

	Included (n = 14 122)	Excluded (n = 981)
Child gender boy (%)	51.2	48.9 [978]
Daily smoking (%)	11.0	23.1 [26]
Education (years)	14.4 ± 2.4 †	14.4 ± 2.4
Homemaker (%)	30.2	27.6 [261]
Maternal age (years)	33.0 ± 4.6	32.9 ± 4.5
Maternal BMI	24.8 ± 4.4	24.7 ± 3.8
Single marital status (%)	6.0	10.1 [238] ‡

^* Number of cases in brackets.

^{† †} Mean (standard deviation) (all such values).

^‡ Significantly different from the included cases (χ² test): P < 0.05. BMI, body mass index.