Smoking cigarettes throughout pregnancy is one of the single most important avoidable causes of adverse pregnancy outcomes, resulting in severe short- and long-term negative effects for the mother and the unborn child (Mund et al, 2013). The harmful effects include premature delivery, low birthweight (Räisänen et al, 2014), and detrimental effects on the placenta, including tissue necrosis and fibrosis (Klesges et al, 1998), and intrauterine growth retardation (Bickerstaff et al, 2012). There is also an increased likelihood of the baby developing congenital abnormalities, with a higher incidence of facial, pulmonary, heart, gastrointestinal and renal malformations (Mund et al, 2013). Fetal neuronal development is also compromised (Julvez et al, 2007), with impairment of cognitive and verbal skills, leading to challenging behavioural traits (Yang et al, 2013).
There have been numerous intensive interventions to get more women to quit smoking as early as possible into their pregnancy. Consequently, a high proportion of smokers do stop once they realise they are pregnant, but about 40% of smokers, largely poorly educated and socioeconomically disadvantaged women, continue to smoke throughout the pregnancy (Health and Social Care Information Centre, 2013).
Interventions
Nicotine replacement therapy
One area of intervention is the use of nicotine replacement therapy (NRT). This comes in different forms, including: skin patches, which are slow release, and chewing gum, inhalators, tablets, strips and lozenges, nasal spray and mouth spray; all of which are rapid release. It is well established that NRT can double the quit rate over placebo in the general population, especially when long and short-acting formulae are used in combination (Brose, 2013), but still the success rate of achieving abstention beyond 4 weeks is modest. This is largely due to failure to complete the programme and low acceptance of the products’ efficacy. A recent evaluation of NRT in pregnancy found little effect in achieving long-term abstinence (Cooper et al, 2014).
Electronic cigarette
An alternative nicotine delivery system is the electronic cigarette (e-cigarette). These are battery-powered atomisers that heat liquid nicotine dissolved in propylene glycol with added flavourings. The resulting ‘smoke’ is largely water vapour, without the carbon monoxide and tar-based carcinogens and free radicals that are responsible for many of the smoking-related effects during pregnancy. Depending on the brand, each nicotine cartridge is designed to produce about 250–400 puffs, equivalent to 1-2 packs of combustible tobacco cigarettes.
E-cigarettes are now aggressively marketed as an alternative to conventional tobacco cigarettes, although very little is known about the health consequences of their long-term use (Besaratinia and Tommasi, 2014), especially during pregnancy; yet many users regard them as a safer alternative to conventional cigarettes (Tan and Bigman, 2014). In the last 3 years these products have become very popular, with over 2 million users in the UK, and because of their unregulated status they are freely available and do not carry excise duty, so provide a cheaper alternative to cigarettes.
The manufacturing processes of the different brands are extremely variable, with differing amounts of nicotine and efficiency of delivery and irregular levels of additives—some of which are potentially toxic. Also, because of their rapid emergence, the clinical information about their use as a smoking cessation aid is limited, although a study of e-cigarette users found a higher reported continued abstinence than those who used a licensed NRT product bought over-the-counter (Brown et al, 2014).
Many of the harmful effects of smoking are directly attributed to nicotine, both to the mother and to the fetus. Nicotinic cholinergic receptors previously thought to be restricted to nervous tissue have been found in the membranes of non-neurological cell types including immune cells, the airways, gastrointestinal tract and in the normal healthy human placenta, where their stimulation through maternal smoking can influence cell growth and protein synthesis, specifically leading to defective fetal development of the nervous system (Lavezzi et al, 2014) and vasoconstriction within the placenta leading to restricted tissue growth and necrosis (Machaalani et al, 2014).
Although e-cigarettes are promoted as smoking cessation aids, many smokers are using them as an acceptable alternative nicotine delivery system; with many users continuing to use normal cigarettes when they can. Consequently, e-cigarettes are potentially harmful to both mother and baby during pregnancy and should not be recommended. However, they do not contain carbon monoxide, or the many of the other harmful toxins, so are probably a safer alternative to combustible cigarettes. Women who report using e-cigarettes should be warned of the dangers of nicotine to their baby and that e-cigarettes are not endorsed for use during pregnancy. They should be advised if they are used at all to use them sparingly and that a gradual reduction of use could assist and achieve complete abstinence.
There is a dilemma, if e-cigarettes reduce the use of normal cigarettes should they be permitted or do we prevent their use knowing that many women will continue to use normal cigarettes as well?