Professor Linda Bauld
Professor of Health Policy at the University of Stirling and Cancer Research UK’s cancer prevention champion
Smoking in pregnancy remains the leading preventable cause of neonatal and maternal mortality in the UK. Many women who smoke give up before they become pregnant or in early pregnancy, but around 1:4 in the UK continue to smoke for some of the pregnancy and 1:8 continuously.
Women should be supported to stop smoking completely during pregnancy, by referral to NHS smoking cessation services which are available across Scotland, and can safely use nicotine replacement therapy to do so. There is little evidence that cutting down is beneficial.
The main reason for this is compensatory smoking, where women inhale more deeply and smoke more of each cigarette to get the nicotine they need, even if they have cut down. It is not the nicotine that is harmful per say, but the many toxicants (known as ‘tar’) in cigarettes.
E-cigarettes are not currently licensed as stop smoking medications and therefore can’t be explicitly recommended for use during pregnancy. There is growing evidence of their potential promise to support smoking cessation in non-pregnant populations and both the Medicines Healthcare Regulatory Agency and the National Institute of Health and Care Excellence have made clear that these devices are less harmful than continued tobacco use.
Thus, despite the lack of data of safety in pregnancy, we can be relatively confident that if the choice is between continued smoking and use of an e-cigarette (‘vaping’) then vaping is the safer option. 
The National Centre for Smoking Cessation and Training guidance  for midwives and other health professionals states “if a woman reports that she has stopped tobacco completely but is using an e-cigarette, she should be congratulated and encouraged to stay away from all tobacco use, even if that involves continuing to use an e-cigarette to avoid relapsing to smoking”.
The priority is to encourage and support pregnant women to move away from tobacco, and some women may find that e-cigarettes help them to do this.