Exposure to Nicotine During Pregnancy
Exposure to nicotine during pregnancy: reviewing exposure outcomes, advances in management strategies and areas needing improvements
Introduction
Nicotine is an alkaloid molecule primarily derived from a plant family (Solanaceae, also known generally as nightshades). It is a potent chemical producing parasympathomimetic effects and is widely abused as a stimulant too (Mishra et al., 2015, Pubchem, 2020). It is also the major component of the tobacco and tobacco containing products, the most common of which are cigarettes and cigars with cigars containing nicotine roughly the amount of a pack of cigarettes in a single one. Apart from its direct or active users, it also passively affects non-smokers via inhalation of the secondhand smoke who are present in the smoking environment (Naeem, 2015, Salimzadeh et al., 2016).
Nicotine exposure can be a major cause of many of the neurodevelopmental as well as behavioral abnormalities which can have implications at all stages from infancy through adulthood in human beings (Wickström, 2007, McCarthy et al., 2020). The most evident cause of this is the prenatal exposure via mothers during pregnancy. The main mechanism of its action is through the interaction with the acetylcholine receptors of the brain cells and hence interfering and modifying the timing of these receptors neuronal action (Atluri et al., 2001). As it’s addiction prevents poses difficulty for many pregnant women in the cessation of its use, the main purpose of this review is to first to have a critical look at the its exposure to pregnant women, and then to focus on its management strategies and gaps in research which need attention in this area.
Search methodology
The search methodology followed for this critical review was started with the help of instructions provided in the lecture. To jump start, general searches about the chemical, its nature and involvement for human health was done. After getting an overview, more specific searches were done related to mother smokers and their babies getting affected. At this point, the write up was started and the rest of the searches were done intuitively based on the question which keep popping in the mind as the write up was being done.
Body of review
Consequences of nicotine exposure to pregnant women
Cigarette smoking is the most common route of nicotine exposure. During pregnancy, it can lead to a multitude of abnormalities and health problems for babies which include preterm births (Soneji and Beltrán-Sánchez, 2019), defects of mouth and lips of babies (Lie et al., 2008, Ozturk et al., 2016), and an increased risk of sudden infant death syndrome (SIDS) (Milerad and Sundell, 1993). A major reason for continued smoking during pregnancy and an inability to quit has been found to be associated with one’s personality traits (Leszko et al., 2020). This remained an unexplored avenue for the past, but now it is gaining increasingly more attention especially in reference to the pregnant women.
Besides neurological complications, infants and newborns are also at high risk of lung developmental and respiratory diseases. This is particularly associated with the increasing use of E-cigarettes especially by pregnant women due to the advertisements implicating their safe nature as compared to the traditional ones. The 50% general incidence of continued smoking during pregnancy is ultimately manifested in the decreased pulmonary function of the infants, continuing their lifetimes. This has been corroborated by a study involving 8800 children of age 8-12 years, who displayed reduced forced expiratory flows (FEF) when their mothers used to smoke during pregnancy. Further complications also included altered tidal breathings. This has been also substantiated by a cell based study in which vapors of the E-cigarettes have been inducing an inflammatory response in the bronchial epithelial cells (Filion et al., 2011, Hayatbakhsh et al., 2009, Cunningham et al., 1994, Herr et al., 2020).
Cognitive effects in infants and babies
The well-known effects of nicotine exposure during pregnancy include under-weight infants and increased rate of mortality and morbidity. Also, an increase in the pulmonary infection rate of the babies has also been observed consequentially. While some epidemiological studies have also pointed towards the increased risk and incidence of cancer in the babies (also during the adult life time) of the active smoker mothers, the same is ambiguous about the passive smokers’ infants or children (Schulte-Hobein et al., 1992). A link has also been found to be present between deficits in IQ, memory and learning of the children and maternal smoking during pregnancy (Fried et al., 2003).
Since nicotine acts via binding with the nicotinic acetyl choline receptors present in the neuronal cells of both the peripheral as well as central nervous system, but limited success has been achieved in linking the deficits of cognition with nicotine exposure in animal models (Abdel-Rahman et al., 2005). This can be due to the reason that some of the brain regions involved in cognitive functions are developed during the neonatal stages. However, studies have revealed a change of morphology of the hippocampal cells more that the cerebellar cells as a result of nicotine binding, thus pointing towards a probable involvement of the former in the cognition (Huang et al., 2007). Therefore, deciphering definitive conclusions is pretty challenging for such studies demanding the need or more efficient and relevant models.
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Health outcomes due to nicotine exposure
The long term outcomes of maternal nicotine exposure include various types of behavioral disorders. Most of the associations of nicotine neurotoxicity have been found with the presence of antisocial personality disorder and oppositional defiant disorder, with former being more prevalent in the adulthood and latter equally established from infancy till adulthood (Ernst et al., 2001, Wakschlag et al., 2002). Also, some adoption studies evidenced that a supporting role exists maternal tobacco consumption and the disruptive and defiant behavior of children starting from early childhood. Other neurobehavioral deficits and implications may include anxiety, depression and attention deficit hyperactivity disorder (AHDH) (Gaysina et al., 2013, Estabrook et al., 2016, Ashford et al., 2008).
Besides neuro-behavioral complications, nicotine exposure also leads to pulmonary outcomes leading to lifelong impediments respiratory flow, compliance and tidal patterns of breathing. Major studies on the developmental consequences of nicotine have been done on animal models resulting in similar aftermaths in agreement with the human trials (Hoo et al., 1998, Spindel and McEvoy, 2016). About the repercussions of nicotine during lung development, studies have found an increased expression of alpha-7 nicotinic acetylcholine receptors in the lung fibroblast cells of the fetal monkeys and mice (Sekhon et al., 1999, Wongtrakool et al., 2012). Moreover, DNA methylation changes have also found to be occurring and persisting over several generations due to nicotine exposure (Rehan et al., 2013).
Risk management strategies and measures
Since smoking is the prime cause of nicotine abuse worldwide, policies to help control smoking will be focused here. Of special emphasis will be the use and control of E-cigarettes too, which are increasingly becoming the popular choice of the consumers. World health organization (WHO) has provided a comprehensive and workable measures to manage tobacco use known as MPOWER. Every word of MPOWER describes a measure for tobacco controls which are: M – monitor the use of tobacco, its prevention and pertinent policies; P – protection from smoke; O – offering help in quitting; W – warning about related dangers; E – enforcement of bans on advertisement of tobacco and its products; and R – raised taxes (Organization, 2017, Kalkhoran et al., 2018).
The aspects which can prove to be very useful and constructive in not only providing modifications of the existing policies but also can help formulate new and innovative policies for controlling tobacco use are: history of smoking – as most of the smoking addictions start in early ages; nicotine dependence – a combination of both the physical and behavioral dependence on nicotine; and, factors leading to smoking initiation – socioecological categorization of the factors at different levels starting from individuals and ending at societies, to name but a few of them (Kalkhoran et al., 2018). Together with the WHO’s designed polices, these features can also aid clinicians in treating the smokers at individual levels.
Gaps in scientific knowledge
Although clinical research provides us with very useful information, not only in terms of behavioral and psychological aspects but also tries to cover the socioeconomic, and individual preferences which might be causing nicotine addiction. However, it often proves unsuccessful in conditions when rehabilitated addicted individuals revert back to addition and somehow fail to stick to the clean life despite knowing all the hazards associated with the addiction. Now what causes this retreat is a complex question and hence a major gap in nicotine addiction research which can be explored with the help of animal self-administrations models. These can be utilized not only with different important variables but also can be used to study convergences between preclinical and clinical researches. In this way, it can also prove beneficial for policy makers too, by providing more concrete evidences from experiments and trials as well.
