Table 2.

The development of early-onset and persistent phenotypes of asthma and rhinoconjunctivitis in relation to intensity of maternal smoking during pregnancy

Exposure	Maternal smoking during pregnancy
	Na	na	Crude OR (95% CI)	Adjusted OR (95% CI)b
Early transient asthma
No smoking	6,172	193	Reference	Reference
Total of 1–9 cigarettes/day	446	20	1.39 (0.88, 2.17)	1.53 (1.16, 2.02)
Total of $\ge 10$ cigarettes/day	294	26	2.54 (1.68, 3.85)	2.07 (1.60, 2.68)
Persistent asthma
No smoking	6,172	253	Reference	Reference
Total of 1–9 cigarettes/day	446	19	1.08 (0.70, 1.67)	1.03 (0.78, 1.37)
Total of $\ge 10$ cigarettes/day	294	26	2.25 (1.54, 3.29)	1.66 (1.29, 2.15)
Early transient rhinoconjunctivitis
No smoking	5,489	85	Reference	Reference
Total of 1–9 cigarettes/day	401	5	0.92 (0.43, 2.00)	0.74 (0.44, 1.26)
Total of $\ge 10$ cigarettes/day	283	10	2.27 (1.24, 4.18)	1.94 (1.30, 2.90)
Persistent rhinoconjunctivitis
No smoking	5,489	164	Reference	Reference
Total of 1–9 cigarettes/day	401	21	1.72 (1.14, 2.59)	1.75 (1.32, 2.31)
Total of $\ge 10$ cigarettes/day	283	13	1.83 (1.14, 2.93)	1.55 (1.09, 2.20)

Note: CI, confidence interval; OR, odds ratio.

^aN = total number of exposed children; n = number of exposed cases.

^bORs and 95% CIs obtained from multinomial logistic regression analyses adjusted for sex, parental education level, parental allergy, older siblings, breastfeeding, study center, intervention arm, and early day-care attendance.