Table 3.

Maternal periconceptional exposure to cigarette smoke and limb deficiencies, National Birth Defects Prevention Study (1997–2007)

Cigarette smoking exposure	Controls (n = 8352)		Any LD (n = 906)
	No.	%	No.	%
Any active or passive
No active or passive	5664	68.0	589	65.3
Active or passive	2666	32.0	313	34.7
Any active
No active or passive	5664	78.7	589	75.7
Activea	1537	21.3	189	24.3
Any passive (home)
No active or passive	5664	82.2	589	79.1
Passive (home)b	1231	17.9	156	20.9
Any passive (work)
No active or passive	5664	83.2	589	81.6
Passive (work)c	1148	16.9	133	18.4
Type of smoke
No active or passive	5664	68.1	589	65.3
Active only	626	7.5	73	8.1
Passive only (home or work)	1126	13.5	124	13.8
Active and passive	906	10.9	116	12.9
Cigarettes/daya
No active or passive	5664	78.8	589	75.8
1–14/day	1270	17.7	154	19.8
≥15/day	253	3.5	34	4.4
Duration of active smoking
No active or passive	5664	78.7	589	75.7
1 month	217	3.0	26	3.3
2 months	324	4.5	42	5.4
3 months	177	2.5	20	2.6
4 months	819	11.4	101	13.0
Duration of passive (home) smoke
No active or passive	5664	73.6	589	71.1
1 month	139	1.8	10	1.2
2 months	116	1.5	14	1.7
3 months	95	1.2	10	1.2
4 months	1685	21.9	206	24.9

No., number of cases or controls.

Numbers vary because of incomplete or missing data. Due to rounding, percentages may not total 100.

^aMay include mothers who report exposure to passive (home or work) cigarette smoke.

^bMay include mothers who report exposure to active or passive (work) cigarette smoke.

^cMay include mothers who report exposure to active or passive (home) cigarette smoke.