Table 1.

Population characteristics in relation to parental smoking

	total n = 3,564	no parent smokes n = 2,759	at least one parent smokes n = 805
mean birth weight of the child (gr.)	3515 (543)	3536 (534)	3444 (568)	*
mean age of the mother (sd)	30.5 (3.8)	30.6 (3.8)	30.2 (4.1)	*
mean age of the father (sd)	32.8 (4.5)	32.9 (4.5)	32.7 (4.7)
male gender of the child (%)	51.7	51.8	51.2
mean number of older siblings	0.70 (0.87)	0.69 (0.87)	0.74 (0.87)
% breastfed for at least 8 weeks	60.9	65.1	46.6	*
% with allergic mother	28.9	29.9	25.5	*
% with allergic father	30.5	32.2	24.7	*
education mother (%)
low (level 1 or 2)	12.1	9.2	22.0	*
middle (level 3,4 or 5)	52.0	50.4	57.4	*
high (level 6 or 7)	35.1	39.7	19.4	*
education father (%)
low (level 1 or 2)	18.4	15.5	28.1	*
middle (level 3,4 or 5)	40.4	38.8	45.8	*
high (level 6 or 7)	39.4	44.0	23.6	*
ethnicity mother (%)
born in Netherlands and Dutch ethnicity	92.4	92.6	91.8
born in Western country and Dutch or Western ethnicity	1.9	2.0	1.6
not born in Western country or non-Western ethnicity	3.2	3.0	4.1
ethnicity father (%)
born in Netherlands and Dutch ethnicity	91.1	91.8	88.5	*
born in Western country and Dutch or Western ethnicity	1.8	1.7	2.2
not born in Western country or non-Western ethnicity	4.4	3.8	6.3	*

sd: standard deviation

* significant difference between no smoking parent or at least one smoking parent; p < 0.05