Background Infant neurobehaviour provides an insight into the development of the central nervous system during infancy, with behavioural abnormalities highlighting a cause for concern. Research has demonstrated that prenatal exposure to cigarettes leads to deficits within neurobehavioural development, along with negative birth outcomes detrimental to subsequent development. With the growing use of e-cigarettes amongst pregnant women, this study explores how prenatal e-cigarette exposure compares to prenatal cigarette exposure. Methods Eighty-three infants were involved in the study, either exposed prenatally to cigarettes or e-cigarettes or not exposed to either. Differences were assessed between these three groups for birth outcomes and scores on the Neonatal Behavioural Assessment Scale (NBAS) at one month of age. Findings 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. Interpretation To our knowledge, this is the first research study assessing a neurological outcome as a result of e-cigarette exposure. Findings of this have potentially important implications for public health policies regarding the safety and use of e-cigarettes throughout pregnancy. Funding This research was funded by a doctoral training partnership scholarship via the ESRC, ES/P000762/1.

Of clinical importance is the finding that although fetuses are affected by maternal mental health in general here we demonstrate, using eye-blink-rate during stimulation as measure of neuro-development, that fetuses are differentially affected by maternal anxiety and depression with anxiety increasing and depression decreasing fetal reactivity significantly.

Prenatal exposure to cigarette smoke has lasting postnatal effects including significant increased risk of cognitive impairment and learning difficulties. 1-3 Research suggests two specific toxins in cigarettes are causing these effects, namely carbon monoxide and nicotine. Carbon monoxide crosses the placenta binding to haemoglobin leading to a reduction in blood flow, ultimately impacting brain development and growth. 4 Similarly, nicotine readily crosses the syncytium, a thin layer of tissue separating maternal and foetal blood. 5 Although the foetal brain is protected from a range of neurotoxins, it is specifically sensitive to nicotine which targets specific neurotransmitters, leading to cell abnormalities and impaired foetal brain development by affecting synaptic activity. 5 Since nicotine affects brain development, it has the potential to affect neurobehaviour 6 including levels of excitability, negative affect, social orientation and regulation in infants. 7 However, there are a number of potential confounding factors that may influence human infant neurobehaviour, leading to difficulties in underpinning the contribution of cigarettes on the neurobehavioural outcome. Therefore, animal models provide an experimental paradigm to define the mechanisms of nicotine on neurobehaviour.

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Aim To assess whether foetal mouth movement frequency changes across gestation and whether there are differences between cigarette and e‐cigarette exposure conditions in comparison to a non‐exposed group of foetuses. Method Pregnant women underwent 4‐dimensional (4D) foetal ultrasound scans at 32 weeks (106 scans) and 36 weeks of gestational age (87 scans) at James Cook University Hospital, UK. The 4D scans were coded using the Fetal Observable Movement System (FOMS). Measures of maternal smoking status, stress, depression, anxiety, attachment and time of scan were also collected. There were four exposure groups: non‐smokers, light smokers (<10 per day), heavy smokers (11–20 per day) and e‐cigarette users. Results No significant differences in relative frequency of mouth movements between the exposure groups at 32‐ and 36 weeks of gestational age were found. Foetal mouth movements declined from 32 to 36 weeks of gestation for non‐exposed and e‐cigarette‐exposed foetuses. Conclusion Due to variability in foetal behaviour, examining mouth movements alone may not be the most appropriate method for assessing group differences. However, in line with other research, mouth movement frequency declined between 32‐ and 36 weeks of gestational age. A combination of foetal behavioural assessments is needed to assess the effects of cigarette and e‐cigarette exposure on foetal neurobehavioural development.