Table 2. Characteristics associated with vaping in pregnancy.

Characteristics	Vaping/Total1	Proportion vaping (%)2	Unadjusted		Adjusted for smoking pattern only		Adjusted for sociodemographic characteristics only3		Adjusted for smoking pattern and sociodemographic characteristics4
			Risk ratio (95% CI)2	p-value	Risk ratio (95% CI)2	p-value	Risk ratio (95% CI)2	p-value	Risk ratio (95% CI)2	p-value
Age of woman, per year	_	_	0.91 (0.88 to 0.94)	<0.001	0.97 (0.94 to 1.00)	0.081	0.94 (0.91 to 0.98)	0.001	0.98 (0.95 to 1.01)	0.133
Age when left full-time education
16 years or less	25/479	5.30	3.02 (1.95 to 4.67)	<0.001	1.01 (0.65 to 1.57)	0.936	1.83 (1.15 to 2.92)	0.029	0.92 (0.58 to 1.44)	0.915
17 to 18 years	32/1,033	4.00	2.28 (1.52 to 3.41)		1.07 (0.72 to 1.59)		1.55 (1.01 to 2.36)		0.99 (0.66 to 1.49)
19 years or more	41/2,867	1.76	ref.		ref.		ref.		ref.
Country of birth
Non-UK	11/1,009	1.21	ref.	<0.001	ref.		ref.	0.003	ref.	0.352
UK	88/3,412	3.51	2.90 (1.71 to 4.92)		1.33 (0.79 to 2.23	0.282	2.32 (1.34 to 4.01)		1.28 (0.76 to 2.17)
Index of multiple deprivation (IMD)
1 (most deprived)	28/693	4.60	2.19 (1.23 to 3.90)	0.001	1.10 (0.61 to 1.98)	0.389	1.75 (0.94 to 3.25)	0.039	1.06 (0.59 to 1.92)	0.648
2	18/852	2.32	1.11 (0.57 to 2.13)		0.74 (0.39 to 1.42)		0.99 (0.50 to 1.95)		0.76 (0.40 to 1.45)
3	16/929	2.20	1.05 (0.53 to 2.09)		0.77 (0.39 to 1.51)		0.95 (0.47 to 1.91)		0.78 (0.40 to 1.53)
4	18/981	2.09	0.99 (0.49 to 2.02)		0.80 (0.40 to 1.60)		0.91 (0.44 to 1.87)		0.80 (0.40 to 1.61)
5 (least deprived)	19/966	2.10	ref.		ref.		ref.		ref.
Living with partner
No	13/313	4.83	ref.	0.001	ref.	0.193	ref.	0.976	_	_
Yes	86/4,108	2.47	0.51 (0.35 to 0.76)		1.30 (0.88 to 1.92)		0.99 (0.65 to 1.51)		_
Parity
Primiparous	49/2,284	2.53	ref.	0.292	_	_	_	_	_	_
Multiparous	50/2,137	3.07	1.21 (0.85 to 1.73)		_		_		_
Smoking pattern
Never-smoker	5/2,942	0.30	0.09 (0.04 to 0.20)	<0.001	_	_	_	_	0.09 (0.04 to 0.20)	<0.001
Ex-smoker	22/880	3.33	ref.		_		_		ref.
Pregnancy-inspired quitter	21/246	7.65	2.40 (1.37 to 4.20)		_		_		2.16 (1.22 to 3.84)
Temporary quitter	13/137	9.48	2.91 (1.60 to 5.28)		_		_		2.51 (1.35 to 4.66)
Persistent smoker	37/192	17.73	5.47 (3.47 to 8.62)		_		_		4.49 (2.71 to 7.45)

¹Unweighted

²Weighted

³Adjusting for sociodemographic characteristics (age of woman, country of birth, education, IMD quintile and living with partner) for which there is some evidence of unadjusted association with vaping

⁴Adjusting for smoking pattern in pregnancy, in addition to age of woman, country of birth, education and IMD quintile which are still associated with vaping after adjustment for sociodemographic characteristics only

Adjusted estimates are not reported if there is no evidence of association in the unadjusted or adjusted estimate in the previous step of sequential adjustment