Table 2 Young adult smoking patterns by three mutually exclusive categories of maternal smoking status.

Young adults smoking pattern reported at 21 years	n	Maternal smoking status in the three mutually exclusive categories			p Value*
		Never smoked (n = 1623)	Smoked before or after pregnancy but NOT during pregnancy (n = 348)	Smoked before, after and during pregnancy (n = 1087)
Onset of smoking					<0.001
Never smoked	1568	57.21	50.29	42.78
Early onset	441	11.53	17.24	17.85
Late onset	1048	31.26	32.47	39.37
Smoking category					<0.001
Never smoked	1563	57.18	50.00	42.41
Used to smoke/smoke occasionally	761	24.89	28.45	23.74
Smoke regularly	734	17.93	21.55	33.85
Smoking patterns					<0.001
Never smoked	1570	57.24	50.29	42.87
Early onset and used to smoke or smoked occasionally	196	6.28	8.91	5.80
Early onset and smoked regularly	244	5.24	8.33	11.96
Late onset and used to smoke or smoked occasionally	558	18.55	19.25	17.48
Late onset and smoked regularly	490	12.69	13.22	21.90

*Three smoking categories were compared by computing a χ² test.