Table 1.

Characteristics of sample by women's smoking status

Characteristicsa	Total		Nonsmokerb		Smokerb		P valuec
	N %	(95 % CI)	N	%	N	%
Total	3,427	100	2,292	69.8	991	30.2
Age (years)
≤19	581	17.2 (15.0–19.4)	398	17.6	159	16.3	0.5241
20–34	2,390	70.6 (68.2–73.1)	1,584	69.9	706	72.2
≥35	412	12.2 (10.7–13.6)	284	12.5	113	11.5
Foreign citizenship
Yes	228	6.7 (3.8–9.6)	202	8.9	20	2.0	0.0010
No	3,173	93.3 (90.4–96.2)	2,073	91.1	966	98.0
Marital status
Married or partnered	2,896	85.4 (82.7–88.1)	1,976	87.0	764	82.2	0.0018
Unmarried	494	14.6 (11.9–17.3)	295	13.0	129	17.8
Highest level of education
Incomplete primary school or less	220	6.4 (4.4–8.5)	150	6.6	64	6.5	0.0002
Completed primary school	939	27.6 (23.1–32.1)	586	25.7	328	33.2
Incomplete secondary school	1,571	46.2 (39.4–52.9)	1,025	45.0	465	47.1
Completed secondary or more	673	19.8 (13.0–26.6)	515	22.6	131	13.2
Work status in past year
Employed or student	780	23.6 (17.8–29.4)	507	22.9	234	24.3	0.5499
Unemployed	2,530	76.4 (70.6–82.2)	1,706	77.1	727	75.7
Parity
0	1,118	34.5 (31.4–37.7)	790	36.5	282	29.9	0.0050
≥1	2,118	65.5 (62.3–68.6)	1,375	63.5	602	70.1
Initiation of prenatal care
First trimester	1,676	52.3 (45.8–58.7)	1,126	52.4	480	51.8	0.7431
Second trimester	1,269	39.5 (34.9–44.2)	840	39.1	377	40.7
Third trimester	262	8.2 (5.4–10.7)	183	8.5	70	7.5

CI confidence intervals

^aSample size varied by each item due to missing values, ranging from 0.7 % (education) to 6.4 % (initiation of prenatal care)

^bSmoking status was missing for 144 women (4.2 %)

^cChi square tests were used to assess differences between nonsmokers and smokers