Table 2.

Smoking Behaviors

	Never smokers N=748,055	Quit in the 1st trimester N=57,017	Quit by the 2nd trimester N=23,278	Quit by the 3rd trimester N=9,515	Smoked throughout pregnancy N=141,333
Preconception Smoking Behaviors
Average Number of Cigarettes Smoked per Day	0	11.8 ± 9.7	14.6 ± 10.4	16.2 ± 9.8	17.1 ± 9.9
Smoke ≥ 1 ppd (≥20 cigs/day)	0%	17,822 (31.3%)	10,280 (44.2%)	5,035 (52.9%)	81,072 (57.4%)
Pregnancy Smoking Behaviorsa
		Preconception	1st Trimester	2nd Trimester	3rd Trimester
Average Number of Cigarettes Smoked per Day	0	11.8 ± 9.7	9.0 ± 8.1	7.2 ± 7.2	10.0 ± 7.5
< 10	0.0%	22,209 (39.0%)	12,613 (54.2%)	6,285 (66.1%)	60,797 (43.0%)
10–19	0.0%	16,986 (29.8%)	6,304 (27.1%)	2,137 (22.5%)	52,594 (37.2%)
≥ 20	0.0%	17.822 (31.3%)	4,361 (18.7%)	1,093 (11.5%)	27,942 (19.8%)

All comparisons are statistically significant at p-value ≤0.001 for the X² statistic corresponding to the 5 smoking group comparison for each maternal characteristic in this table.

Dichotomous variables are presented as percent of n for corresponding smoking group.

Continuous variables are presented as mean ± standard deviation.

^aEach column represents the smoking behavior in the final 3 months of smoking

Quit in the 1^st Trimester = ≥1 cig/day in the 3 months before pregnancy and 0 cig/day in the 1^st, 2^nd, & 3^rd trimester

Quit by the 2^nd Trimester = ≥1 cig/day in the 3 months before pregnancy & in the 1^st trimester and 0 cig/day in the 2^nd and 3^rd trimester

Quit by the 3^rd Trimester = ≥1 cig/day in the 3 months before pregnancy, 1^st trimester, & 2^nd trimester and 0 cig/day in the 3^rd trimester

Smoked throughout pregnancy = ≥1 cig/day in all categories