TABLE 1.

Maternal smoking during pregnancy and the risk of asthma in children.

Smoking exposure	Age	Relative risk Odds ratio (95% CI)		References
		Male	Female
Smoker at some stage	14 years	1.15 (1.01–1.72)	1.25 (0.85–1.22)	Alati et al., 2006
>20 cigarettes (early and late)	14 years	0.57 (0.20–1.60)	1.09 (0.47–2.51)	Alati et al., 2006
Total of 1–9 cigarettes/day	4–16 years	1:19 (0.98–1.43)		Thacher et al., 2018
<10 Cigarettes per day	7 years	1.20 (1.04–1.38)		Jaakkola and Gissler, 2004
Total of ≥10 cigarettes/day	<5 years	1.68 (1.10–2.58)		Martinez et al., 1992
>10 Cigarettes per day	7 years	1.31 (1.09–1.58)		Jaakkola and Gissler, 2004
Total of ≥10 cigarettes/day	4–16 years	1:66 (1.29–2.15)		Thacher et al., 2018
Smoking during pregnancy	First 3 years	1.88 (1.14–3.12)		Murray et al., 2004
Smoking during pregnancy	4–6 years	1.65 (1.18–2.31)		Neuman et al., 2012
Smoking during pregnancy	2–7 years	1.7 (1.2–2.2)		Harju et al., 2016
Smoking during pregnancy	5–9 years	0.97 (0.51–1.84)		Sherman et al., 1990
Smoking during pregnancy	14 years	1.49 (0.91–2.45)		Hollams et al., 2014
Smoking during pregnancy	7–16 years	0.99 (0.78–1.25)		Strachan et al., 1996