TABLE 4.

JOINT EFFECTS OF ACTIVE SMOKING AND EXPOSURE TO MATERNAL SMOKING DURING PREGNANCY ON NEWLY DIAGNOSED ASTHMA, RELATIVE RISK AND 95% CONFIDENCE INTERVAL, CHILDREN'S HEALTH STUDY 1993–2003

		Maternal Smoking During Pregnancy		Interaction
		Unexposed	Exposed	p Value
Frequent regular smoking*	No	1	0.9 (0.5, 1.4)	0.02
	Yes	1.2 (0.4–4.0)	8.8 (3.2–24.0)

Relative risks (Hazard ratios) and corresponding 95% confidence intervals were obtained from Cox's proportional hazard model with separate baseline hazard for sex and age (in yr) at study entry. All models are adjusted for race/ethnicity, community, maternal smoking during the children's postnatal period, and numbers of other smokers in the home.

^*Smoking at least seven cigarettes in the last week.