Table 1.

Characteristics of women who quit smoking during pregnancy.

	Total (n = 10,917)		Cessation (n = 10,300)		Relapse (n = 617)		p
	n	%	n	%	n	%
Maternal age at delivery (yrs)
<20	145	1.3	127	1.2	18	2.9	<0.0001
20–24	1726	15.8	1615	15.7	111	18.0
25–29	3594	32.9	3403	33.0	191	31.0
30–34	3321	30.4	3168	30.8	153	24.8
35–39	1834	16.8	1716	16.7	118	19.1
≥40	297	2.7	271	2.6	26	4.2
Maternal education (yrs)
≤12	6183	56.6	5740	55.7	443	71.8	<0.0001
≥13	4734	43.4	4560	44.3	174	28.2
Household income (million JPY)
<2	1040	9.5	960	9.3	80	13.0	<0.0001
2–3	4902	44.9	4591	44.6	311	50.4
4–5	3162	29.0	2999	29.1	163	26.4
6–7	1136	10.4	1098	10.7	38	6.2
≥8	677	6.2	652	6.3	25	4.1
Pre-pregnancy BMI (kg/m2)
<18.5	1865	17.1	1764	17.1	101	16.4	0.015
18.5–24.9	7675	70.3	7260	70.5	415	67.3
≥25	1377	12.6	1276	12.4	101	16.4
Fertility treatment
No	10568	96.8	9962	96.7	606	98.2	0.040
Yes	349	3.2	338	3.3	11	1.8
Status of multiple birth
Single birth	10845	99.3	10232	99.3	613	99.4	0.972
Multiple birth	72	0.7	68	0.7	4	0.6
Parity
First	5586	51.2	5369	52.1	217	35.2	<0.0001
≥Second	5331	48.8	4931	47.9	400	64.8
Feeding method at 1 month after delivery
Breast milk	5150	47.2	4961	48.2	189	30.6	<0.0001
Breast and formula milk	5071	46.5	4783	46.4	288	46.7
Formula milk	696	6.4	556	5.4	140	22.7
Partner smoking status during pregnancy
Non-smoker	1138	10.4	1085	10.5	53	8.6	0.001
Quitter before pregnancy	827	7.6	794	7.7	33	5.4
Quitter during pregnancy	840	7.7	808	7.8	32	5.2
Smoker	8112	74.3	7613	73.9	499	80.9
Number of cigarettes use per day
1–10	7020	64.3	6716	65.2	304	49.3	<0.0001
≥11	3897	35.7	3584	34.8	313	50.7
Maternal drinking status at 1 months after delivery
Non-drinker	10122	92.7	9646	93.7	476	77.1	<0.0001
Drinker	795	7.3	654	6.3	141	22.9
EPDS score
<9	8894	81.5	8420	81.7	474	76.8	0.002
≥9	2023	18.5	1880	18.3	143	23.2
Spent at parents’ home after delivery
Did not spend or <14 days	6108	56.0	5691	55.3	417	67.6	<0.0001
≥14 days	4809	44.1	4609	44.8	200	32.4

BMI, Body Mass Index; EPDS, Edinburgh Postnatal Depression Scale.