Experts Comment on Study Analysing Effects of Smoking and Vaping in Pregnancy 

Titled, “The effects of prenatal cigarette and e-cigarette exposure on infant neurobehaviour: A comparison to a control group,” the study explored how prenatal e-cigarette exposure compares to prenatal cigarette exposure, in terms of birth outcomes, neurological development and subsequent behavioural abnormalities.

The researchers followed eighty-three infants, who were either exposed prenatally to cigarettes or e-cigarettes, or not exposed to either. The differences amongst these groups were assessed by observing measurable birth outcomes and scores on the Neonatal Behavioural Assessment Scale (NBAS) at one month of age.

“Both cigarette and e-cigarette exposed infants had a significantly greater number of abnormal reflexes. For both self-regulation and motor maturity, cigarette exposed infants performed significantly worse with e-cigarette exposed infants having decreased motor maturity abilities and marginally decreased for self-regulation. Birth outcomes, namely birth weight, gestation and head circumference, did not differ for e-cigarette exposed infants compared with infants who were not prenatally exposed to nicotine. Cigarette exposed infants had a significantly lower birth weight and reduced head circumference in comparison to non-exposed infants,” reported the researchers.

Researchers should always take into account that most vapers are ex-smokers

However, some experts have spoken up in response to these findings, voicing some concerns about their reliability. Professor of Behavioural Science and Health, and Director of the Tobacco and Alcohol Research Group at UCL, Prof. Jamie Brown, pointed out that given that most vapers are previous smokers, the study should have looked into the smoking history of all the vaping participants.

“It is well-established that cigarette smoking during pregnancy increases the risk of a range of health problems. It is important to establish the risk of e-cigarettes compared with cigarettes during pregnancy. This requires studies to conduct a detailed assessment of both these behaviours during pregnancy.”

“We know that most e-cigarette users have previously smoked.  It is not clear from this article how much the 10 parents who switched to e-cigarettes by 32 weeks had smoked before that point nor the extent to which cigarette smoking during the pregnancy may have been responsible for the findings. It is notable that twenty percent of the people using e-cigarettes at 32 weeks in this study had relapsed to cigarette smoking by birth,” explained Brown.

Prof Michael Ussher, Professor of Behavioural Medicine, at the University of London and University of Stirling, voiced similar concerns, and also pointed out a serious error in referring to vaping as smoking.

“A major concern with this study is that the authors only assessed whether the e-cigarettes users had smoked cigarettes in recent hours, rather than also in recent days or weeks. Dual use of cigarettes and e-cigarettes is fairly common in pregnancy and it is possible that the observed harms are due to smoking among those in the e-cigarette group. Also, it is incorrect to use the term ‘smoking e-cigarettes’ as there is no smoke in vapour.  The evidence remains that smoking cigarettes is far more harmful than vaping and vaping may help women to stop smoking.”

Vaping is not smoking

Prof Linda Bauld, Professor of Public Health at the University of Edinburgh, voiced similar concerns as her peers, whilst also highlighting some technical errors. “There are also some questions to be asked about basic errors in the paper. For the demographic information, carbon monoxide (CO) readings are used to validate smoking status and the paper says that this translates to the % of CO in the maternal blood. But CO screening involves a breath test not a blood test.”

In line with Prof Michael Ussher’s arguments, Bauld added that the fact that vaping was referred to as smoking, is a clear indicator that the paper’s peer reviewal process was not thorough. “In addition the authors refer to ‘e-cigarette smoking’ throughout the paper.  There is no smoke or tobacco in e-cigarettes and these devices are not ‘smoked’.  These two features suggest the authors are not familiar with the literature in this area and are issues that should have been picked up when the paper was peer-reviewed.”

A study with multiple errors

Prof John Britton, Emeritus Professor of Epidemiology, University of Nottingham added more errors to the list. “This is a poor study for several reasons – it isn’t randomised; there is no power calculation; there are only 10 e-cig users and two of them reverted to smoking before the babies were tested; the paper presents p values instead of effect sizes; some of the outcome scores are clearly not normally distributed (mean – 2SDs is less than 0 in a score with a minimum of zero) but are treated as such; the level of Bonferroni correction for multiple comparisons is not explained (and there are multiple comparisons); and it compares 17 outcomes, three ways, with only 10 (or even really only 8) people in one of the groups.”

“The authors suggest their paper raises the possibility that using nicotine in pregnancy may reduce reflex responses in newborn children.  While this remains a possibility, if their study does suggest this then it also demonstrates clearly that babies born to mothers who smoke are harmed to a considerably greater extent than any possible harm from nicotine use.  It does not therefore change current advice to pregnant women who smoke, which is to quit all nicotine use if possible but at the very least, stop smoking tobacco.”

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