Table 2.

Weighted distribution of smoking behavior (6 time points), by maternal age Early Childhood Longitudinal Study-Birth Cohort (ECLS-B)

	Age 15–25 (N=3400)	Age 26–35 (N=4400)	Age 36+ (N=1300)	p-value
3 months before pregnancy
Non-smoker	64.7%	81.2%	86.5%	<0.001
Smoking ≤ cigarettes per day (CPD)	8.5%	4.9%	3.6%	<0.001
Smoking 6–10 CPD	13.4%	6.0%	4.6%	<0.001
Smoking >10 CPD	13.4%	7.9%	5.3%	<0.001
Last 3 months of pregnancy
Non-smoker	84.1%	91.0%	93.4%	<0.001
Smoking ≤5 CPD	8.0%	4.0%	2.8%	<0.001
Smoking 6–10 CPD	5.1%	2.9%	3.1%	<0.001
Smoking >10 CPD	2.9%	2.1%	0.7%	<0.001
9 months post-partum
Non-smoker	70.7%	84.5%	89.2%	<0.001
Smoking ≤5 CPD	8.1%	4.7%	3.4%	<0.001
Smoking 6–10 CPD	11.6%	5.3%	3.2%	<0.001
Smoking >10 CPD	9.6%	5.5%	4.2%	<0.001
2 years post-partum
Non-smoker	70.6%	85.1%	90.1%	<0.001
Smoking ≤5 CPD	8.2%	4.3%	2.4%	<0.001
Smoking 6–10 CPD	12.1%	5.0%	3.9%	<0.001
Smoking >10 CPD	9.1%	5.7%	3.6%	<0.001
Child in Preschool
Non-smoker	70.1%	86.0%	90.2%	<0.001
Smoking ≤5 CPD	8.0%	3.5%	1.6%	<0.001
Smoking 6–10 CPD	11.9%	5.1%	3.7%	<0.001
Smoking >10 CPD	10.1%	5.4%	4.5%	<0.001
Child in Kindergarten
Non-smoker	70.5%	88.3%	90.8%	<0.001
Smoking ≤5 CPD	8.7%	3.1%	3.0%	<0.001
Smoking 6–10 CPD	11.7%	3.5%	2.8%	<0.001
Smoking >10 CPD	9.2%	5.2%	3.4%	<0.001