Table 1.

Baseline characteristics of 3,773 women age 18–40 years according to smoking status: The Snart Gravid Cohort, Denmark, 2007 – 2011.^a

	Never Smoker	Current smoker: number of cigarettes/day					Former smoker: time since cessation, years
		<1	1–4	5–9	10–19	≥20	1–1.9	≥2
Number of women	2,346	212	70	146	223	35	135	606
Participant’s age, years (mean)	28.3	28.0	28.1	26.9	27.3	27.5	28.4	29.9
Male Partner’s age, years (mean)	30.8	30.5	29.6	30.9	31.5	32.3	30.9	31.2
Smoking duration, years (mean)	0	10.1	11.8	12.0	12.5	13.7	10.5	7.1
Partner is a regular smoker (%)	11	23	58	60	71	76	16	12
Passive smoking exposure in adulthood (%)	23	49	56	72	83	80	52	36
Participant’s mother smoked while pregnant (%)	34	29	30	43	55	66	35	35
Intercourse frequency ≥4/week (%)	18	16	24	26	29	21	20	17
Doing something to time intercourse (%)	46	46	45	43	46	45	49	49
Body mass index of participant, kg/m2 (mean)	24.0	23.7	24.4	24.4	25.2	25.2	24.4	24.4
Body mass index of partner, kg/m2 (mean)	25.3	25.0	25.8	26.3	26.0	26.0	25.3	25.6
Last contraceptive method: hormonalb (%)	63	64	65	60	64	81	68	57
Parous (%)	31	27	41	43	40	32	21	44
Ever pregnant (%)	41	44	56	66	57	67	39	54
History of infertility (%)	8	7	15	14	13	13	11	9
History of pelvic inflammatory disease (%)	14	15	21	20	25	40	15	17
Regular cycles (%)	76	74	80	76	84	78	74	74
No vocational training or higher education (%)	10	10	11	18	27	25	13	11
Household income <25,000 Danish Kroner/year (%)	13	18	14	17	16	33	14	11
Participant exposure to environmental hazards (%)	17	19	19	22	29	25	26	18
Partner exposure to environmental hazards (%)	22	24	31	34	39	45	30	28
Caffeine intake, mg/day (mean)	108	170	141	184	239	322	160	160
Consumes ≥7 alcoholic beverages/week (%)	8	26	26	10	18	23	16	12

^aAll characteristics except age are age-standardized to the distribution of the cohort at baseline.

^bIncludes oral contraceptive pills and other hormonal contraceptives such as patch and injection.