Topic: The effects of prenatal cigarette and e-cigarette exposure on infant neurobehaviour
Reducing smoking during pregnancy is a key public health priority due to a range of detrimental birth outcomes, including intrauterine growth restriction, low birth weight (<2500 g), small for gestational age, preterm delivery (<37 weeks) and reduced head circumference. Accompanying the birth outcomes, such as low birth weight, are the neurobehavioural deficits that may occur as a result of prenatal cigarette exposure, including irritability, poor muscle tone, decreased self-regulation, increased negative affect and difficult temperament [].
These neurobehavioural deficits have been shown to predict subsequent infant development including psychomotor, cognitive and emotional development. Low birth weight in infants of mothers who smoke indicates fetal growth restriction thought to be related to Carbon Monoxide (CO) exposure affecting the oxygen carrying capacity of the fetal blood []. Alternatives to cigarette smoking, such as nicotine replacement therapy (NRT) and e-cigarettes are therefore considered by some to be a harm reduction method and information provided in healthcare leaflets for pregnant women state that nicotine alone is relatively harmless.
There is however growing concern about the increasing use of e-cigarettes and the safety of nicotine exposure for the developing fetus. Therefore, assessing birth and infant outcomes in fetuses that have been exposed to e-cigarettes, will add to the debate regarding their use during pregnancy.
Although the use of e-cigarettes in pregnancy will not expose the fetus to CO, they will be exposed to nicotine which has been shown to have a negative impact on neurobehaviour. Nicotine has extensive effects on the central nervous system (CNS), with the deficits reflecting the biological and behavioural systems that are modulated through neural feedback.
Later in childhood, exposure to nicotine has been associated to attention deficit hyperactivity disorder (ADHD). However, no research has currently been published to establish the impact of prenatal exposure to e-cigarettes may have on neurobehavioural outcomes of human infants. At present, animal studies have been the main focus emphasizing the negative result of nicotine exposure on brain development, with human infant research yet to be undertaken. Primate models on the effects of nicotine exposure demonstrate that nicotine is highly selective for various brain regions with cell signaling and cell damage occurring leading to disrupted brain development.
Specifically, the cognitive impairments observed are likely to be a result of proliferation and maturation in the medial prefrontal cortex of the progenitor cells leading to a decrease of glutamatergic neurons. This has been shown in primates and rodents are exposed to levels of nicotine comparable to that of an adult smoker, with sufficient amount of nicotine reaching the fetal brain eliciting neurodevelopmental changes, regardless of the gestational time point nicotine is administered.
Due to the critical role of neurobehaviour in an infant’s development and the lack of guidance regarding the effects of e-cigarette use during pregnancy, the present study aims to examine how prenatal exposure to e-cigarettes compares to cigarettes and to no exposure on birth outcomes (i.e. gestation at birth, birth weight and head circumference). Additionally, neurobehavioural outcomes in one-month old infants (i.e. measured using the Neonatal Behavioural Assessment Scale (NBAS) will be reported.
Based on current evidence it is hypothesised that there will be a significant difference in birth outcomes (i.e. shorter gestation, lower birth weight and smaller head circumference) in cigarette exposed compared with non-exposed infants, but no significant differences are expected between e-cigarette exposed infants and non-exposed infants because e-cigarette use in pregnancy is not expected to reduce the oxygen carrying capacity of fetal blood.
Secondly, it is hypothesised, that due to the direct impact of nicotine on brain development, e-cigarette exposed infants will demonstrate a similar pattern of neurobehavioural deficits to cigarette exposed infants. This is the first study assessing the neurobehavioural outcomes of the new-born as a result of nicotine exposure via e-cigarette use.
Topic Discussed: The effects of prenatal cigarette and e-cigarette exposure on infant neurobehaviour