Campbell, K., Cooper, S., Fahy, S., Bowker, K., Leonardi-Bee, J., McEwen, A., …Coleman, T. (2017). ‘Opt-out’ referrals after identifying pregnant smokers using exhaled air carbon monoxide: impact on engagement with smoking cessation support. Tobacco Control, 26(3), 300-306. https://doi.org/10.1136/tobaccocontrol-2015-052662