Table 1 Demographic data on infants from non‐smoking and smoking households.

	Non‐smoking (n = 33)	Smoking (n = 71)	p Value	95% CI*
Sex, n (%)
Male	14 (42)	43 (61)
Female	19 (58)	28 (39)	0.080	−0.02 to 0.37
Birth weight (g), mean (SD)	3607 (600)	3205 (544)	0.002	152 to 652
Gestation (weeks), mean (SD)	39.9 (1.47)	39.6 (1.66)	0.424	−0.42 to 0.98
Feeding, n (%)
Breast fed	24 (73)	17 (24)
Bottle fed	9 (27)	54 (76)	<0.001	−0.64 to −0.29
Social class, n (%)†
I or II	15 (50)	6 (11)
III or IV	5 (17)	10 (18)		−0.61 to −0.05
V or VI	7 (23)	17 (30)		−0.63 to −0.13
VII or VIII	3 (10)	24 (42)	0.002	−0.78 to −0.35
Not known	3	14
Birth order, mean (SD)	1.79 (0.86)	2.66 (1.50)	0.003	−1.43 to −0.31
Age (weeks), mean (SD)‡	10 (2.97)	12 (3.59)	0.090	−2.90 to 0.25
Weight (g), mean (SD)‡	5796 (1053)	5444 (1206)	0.278	−290 to 995

*95% CI for differences in mean values (for continuous variables) or differences in % (categorical variables)

†Social class was based the reported occupation of the highest earner in the household.

‡Measurement taken at time of cotinine estimation.