The trio studied 83 infants as part of the study. They were either exposed prenatally to cigarettes, e-cigarettes, or not exposed to either as the mothers neither smoked nor vaped. They state, “differences were assessed between these three groups for birth outcomes and scores on the Neonatal Behavioural Assessment Scale (NBAS) at one month of age.”
Neurobehavioural responses considered things like the baby’s reflexes such as the ability to grasp a caregiver’s finger and self-regulation looked at things such as the baby being relaxed when held.
- Both cigarette and e-cigarette exposed infants had a significantly greater number of abnormal reflexes (p = ·001; p = ·002)
- For both self-regulation and motor maturity, cigarette exposed infants performed significantly worse (p = ·010; p = ·002), with e-cigarette exposed infants having decreased motor maturity (p = ·036) abilities and marginally decreased for self-regulation (p = ·057)
- Birth outcomes, namely birthweight, 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 birthweight (p = ·021) and reduced head circumference (p = ·008) in comparison to non-exposed infants
Professor Jamie Brown, Director of the Tobacco and Alcohol Research Group at University College London, commented: “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.”
Professor Michael Ussher, Professor of Behavioural Medicine at St George’s, added: “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.”
Linda Bauld has worked with groups looking at pregnant women vaping. The Professor of Public Health at the University of Edinburgh said: “The authors … suggest this might mean that these babies may have signs of impaired brain development and as a result women should not use e-cigarettes in pregnancy. We should be cautious when assuming this study proves that vaping in pregnancy harms babies.
“The first reason to be cautious is that their hypothesis that it is the nicotine in e-cigarettes that may be to blame is not supported by previous research in humans. The large SNAP trial found that young children whose mothers had used nicotine replacement therapy after stopping smoking in pregnancy had normal development up to two years old.
“The second reason is that women who vape in pregnancy are almost universally ex-smokers and it is not uncommon for these women to gradually shift to vaping or even smoke and vape in pregnancy. Vaping was simply self-reported in the study and smoking status was only assessed once at 32 weeks pregnant. It is therefore possible that some or even all of the vaping mothers may have smoked even at low levels at some point during their pregnancy, and if they did this would be a significant confounder, making the results difficult to interpret. The authors do not even mention this important (and likely) limitation in their article.”
“Finally, it is important to note the small size of the vaping group – just 10 women. That sample size is not sufficient to draw firm conclusions.
“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 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.”
The Emeritus Professor of Epidemiology at the University of Nottingham, John Britton, added: “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 new-born 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.”
- “The effects of prenatal cigarette and e-cigarette exposure on infant neurobehaviour: A comparison to a control group” by Froggatt, Reissland, and Covey – [link]