Risks associated with smoking in pregnancy

Tobacco smoking in pregnancy remains one of the few preventable factors associated with complications in pregnancy, such as placental abruption, miscarriage, low birthweight (Kramer 1987), preterm birth (US DHHS 2004; Hammoud 2005; Salihu 2007; Rogers 2009; Vardavas 2010; Baba 2012), stillbirth and neonatal death (Kallen 2001). Tobacco smoking also has serious long‐term health implications for women and infants; 5.4 million people per year currently die from tobacco use, and this is expected to rise to eight million per year in the next 30 years (WHO 2008a). 

Nicotine and other harmful compounds in cigarettes are developmental toxicants (Rogers 2009), which impact on the brain at critical developmental periods (Dwyer 2008) restricting the supply of oxygen and other essential nutrients, fetal growth (Crawford 2008), development of organs (Morales‐Suarez‐Varela 2006), including the lungs (Maritz 2008) and neurological development (Herrmann 2008; Blood‐Siegfried 2010). Growing evidence suggests these 'developmental origins of disease' have life‐long implications (Gluckman 2008).

Young women start smoking for many reasons including: belief it is a rite of passage into adult life, a gesture against authority, trying to appear modern and affluent, or to fit in with social networks (Todd 2001). Tobacco addiction is then caused by nicotine in tobacco which produces a cascade of actions, including release of "pleasure enhancing" dopamine, which strengthens associations of positive feelings with smoking behaviour and appears to be involved in all addictive behaviours (Schmidt 2004). Some suggest the negative feelings of "nicotine hunger" and unpleasant symptoms associated with nicotine withdrawal (Balfour 2004; Hughes 2007) may be stronger for pregnant women due to the physiological adaptations in pregnancy which accelerate nicotine metabolism (Ebert 2009; Ussher 2012a), however a recent study reported less severe withdrawal symptoms among pregnant women in the first 24 hours of abstinence, compared to non‐pregnant women (Ussher 2012b).

Epidemiology of smoking in pregnancy

In high‐income countries, such as Australia, Canada, Denmark, New Zealand, Sweden, the United Kingdom (UK) and the United States (US), the prevalence of smoking in pregnancy has declined from between 20% to 35% in the 1980s to between 10% and 20% in the early 2000s (Cnattingius 2004; US DHHS 2004; Giovino 2007; Dixon 2009b; Tong 2009; Al‐Sahab 2010; Tappin 2010), with significant declines in the last decade bringing the prevalence of smoking in pregnancy well below 10% by 2010 (Lanting 2012). However, the decline has not been consistent across all sectors of society, with lower rates of decline among women with lower socio‐economic status (US DHHS 2004; Pickett 2009; Graham 2010; Johnston 2011b; Lanting 2012). Tobacco smoking in high‐income countries is a marker of social disadvantage and has been cited as one of the principal causes of health inequality between rich and poor (Wanless 2004), and understanding these disparities are central to understanding the tobacco epidemic (Graham 2010).  In Scotland, 30% of women living in the most deprived areas continued to smoke during pregnancy in 2008, compared to 7% in the least deprived areas (Tappin 2010). Women who continue to smoke in pregnancy are more likely to: have a low income, higher parity, no partner, low levels of social support, limited education; access publicly funded maternity care; and feel criticised by society (Graham 1977; Frost 1994; Graham 1996; Tappin 1996; Wakschlag 2003; US DHHS 2004; Ebert 2007; Schneider 2008; Pickett 2009). The World Health Organization (WHO) report into the Social Determinants of Health recognises a paradigm whereby disadvantaged people are more likely to use substances in response to their circumstances (WHO 2008b). There is also a significantly higher prevalence of smoking in pregnancy in several ethnic and aboriginal minority groups (Wiemann 1994; Kaplan 1997; Chan 2001; US DHHS 2004; Wood 2008; Dixon 2009b; Johnston 2011b).  In Australia, smoking during pregnancy is three times more prevalent among Aboriginal and Torres Strait Islander women (53%) than among non‐Aboriginal women (16%) (Johnston 2011b), and similar disparities are reported between Maori and non‐Maori women in New Zealand (Dixon 2009b). These disparities are largely in accord with social and material deprivation. However, in some migrant groups, cultural differences may cut across this social gradient (Troe 2008), which suggests that there are aspects of smoking socialisation not entirely explained by material deprivation.  In the United States, the highest rates of pre‐pregnancy smoking were reported among Alaskan Native women (55.6%), American Indian women (46.9%), and White women (46.4%), with significantly lower rates (less than 20%) reported among African American, Hispanic and Asian‐Pacific women (Tong 2011; Watt 2012). Women who are migrants or refugees to Australia, Canada, New Zealand, Northern Europe, the UK, or the US or who originate from South East Asia also retain a lower prevalence of smoking, despite major social disadvantage (Potter 1996; Small 2000; Bush 2003; Dixon 2009b). However, second‐generation migrant women are more likely to smoke during pregnancy than first‐generation women (Troe 2008), reflecting movement between stages of 'the tobacco epidemic' (Lopez 1994).

In low‐ and middle‐income countries there is marked variation in prevalence of smoking in pregnancy, which reflects the dynamic nature of the tobacco epidemic in these regions (Richmond 2003; Polanska 2004; Bloch 2008).  Smoking rates among pregnant women have been comparatively low (9%) compared to men (50%), due to historical cultural constraints on women's smoking in many low‐ to middle‐income countries (Bloch 2008). However, the prevalence of tobacco smoking among women is increasing and is expected to rise to 20% by 2025, shifting the global tobacco smoking epidemic from high‐income countries to low‐ and middle‐income countries (Samet 2001; Richmond 2003). The highest rates of smoking during pregnancy were reported in Latin America (18.3% in Uruguay 2004 to 2005) (Bloch 2008) and Eastern Europe (15% in Romania 2005 to 2006) (Meghea 2010). Low rates were reported in Pakistan (3%) (Bloch 2008), South East Asia (1.3%) (Barraclough 1999; Ostrea 2008), and China (2% in 1999), though increasing rates among female school children are causing concern (Kong 2008).  In India and Africa, rates of cigarette smoking were low (1.7% and 6.1% pregnant women reporting smoking cigarettes, respectively), (Steyn 2006; Bloch 2008; Palipudi 2009), while use of smokeless tobacco products was high among Indian (4.9% to 33.5%) (Palipudi 2009; Bloch 2008) and African women (6% to 7.5%) (Steyn 2006; Bloch 2008).  The WHO has identified this rise of tobacco use in young females in low‐income, high population countries as one of the most ominous developments of the tobacco epidemic (WHO 2008a), jeopardizing efforts to improve maternal and child health (Cnattingius 2004; Bloch 2008). This increase is being driven by aggressive marketing from tobacco companies, who are predicting high profits from sales in low‐ and middle‐income countries (Kaufman 2001), along with increased tobacco production in these regions (FAO 2003), which further entrenches the countries' tobacco dependence. Marketing strategies are specifically targeted at women and weak regulation of tobacco company marketing has been linked to a rapid increase in smoking among women, particularly those who are vulnerable (Kaufman 2001; Gilmore 2004; Graham 2009). A survey of women's knowledge in two African countries suggests women's knowledge of the risks of tobacco products was extremely limited (Chomba 2010), making women more vulnerable to tobacco marketing.

Issues around smoking in pregnancy are complicated by the intersection of gender (Healton 2009), where a woman's role is seen primarily as a 'reproducer', and emphasis is placed on the rights of the unborn fetus (pxii; World Health Organization 2001). There is a risk these arguments may be used to impose authority over women's behaviour, 'blaming' women for their own plight and that of their children, and using guilt or other means to undermine self‐confidence; further reducing the control women have in their lives (Greaves 2007a).

In addition to the socio‐economic factors associated with continued smoking, there are strong psychological associations, especially with depression and stress (Blalock 2005; Aveyard 2007; Crittenden 2007; Orr 2012), including race‐related stress (Heath 2006; Fernander 2010; Nguyen 2012a). Depressed women are up to four times more likely to smoke during pregnancy than non‐depressed women (Blalock 2005). Despite these strong associations, there is limited information available about the effects of smoking and interventions in pregnant women with psychological symptoms, as they are often excluded from trials (Blalock 2005). Furthermore, while tobacco control initiatives in high‐income countries have been effective in reducing smoking, the stigmatisations of smokers has been an unintended consequence (Burgess 2009; Wigginton 2012), which is being increasingly recognised by the tobacco control community (Farrimond 2006; Thompson 2007a; Burgess 2009). Anti‐smoking campaigns strive to inform, shock or shame people into quitting smoking and rarely take into account low self‐esteem, low self‐efficacy, poverty, stress and increased caring responsibilities that are common among women who continue to smoke during pregnancy (Gilbert 2005). A systematic review of qualitative experiences of women describes how smoking in pregnancy triggered "intense feelings of personal responsibility and inadequacy" and that women's responses to social disapproval varied (Flemming 2013). For some, it provided an incentive to attempt to quit, while among others it resulted in increased smoking, either in response to the stress of social pressure or as an act of rebellion against it (Flemming 2013). Some argue that health risk narratives and the associated social stigma produced through anti‐smoking campaigns contribute to oppression among marginalised people, and a consequence is that these strategies may inspire resistance and resentment rather than compliance (Bond 2012; Wigginton 2012; Flemming 2013).

Although commercial cigarettes are the most prevalent form of tobacco use worldwide, the use of other forms of tobacco (e.g. smokeless tobacco, cigars and pipes, and waterpipes) are becoming more popular in many parts of the world, especially low‐ and middle‐income countries (England 2010). Of particular concern are increasing efforts by the tobacco industry to commercialise and market smokeless tobacco products to young adults (Lambe 2007). In high‐income countries, the use of smokeless tobacco appears to be highly localised among some indigenous groups in Canada and the US, including Lumbee Indian, Navajo, and Alaskan Native communities (Strauss 1997; Spangler 2001; Patten 2009; Kim 2009a; Kim 2010). In India, one‐third (33.5%) of all pregnant women reported using smokeless tobacco (Bloch 2008). In the Democratic Republic of Congo, 6% to 41.8% of pregnant women surveyed reported using other forms of tobacco, primarily snuff (Bloch 2008; Chomba 2010). In South Africa 7.5% of pregnant women surveyed reported using snuff (Steyn 2006). In Iran there has been concern over the 8% prevalence of local waterpipe tobacco smoking among pregnant women (Mirahmadizadeh 2008). These tobacco products may be cheaper and viewed as less harmful than cigarettes (England 2010). In some cases use may be a traditional cultural norm or a medicinal aid to reduce nausea in early pregnancy. However, these products can be high in nicotine content and cause nicotine addiction. Use of these products has been associated with increased oral and pancreatic cancer, and cardiovascular disease (England 2010). There is a paucity of research into the effect of these products on pregnancy outcomes and studies into the effects of these products can be challenging as the chemical content of various toxic compounds is variable and often poorly regulated.  However, limited evidence suggests smokeless tobacco use is associated with decreased birthweight and preterm birth (Verma 1983; Gupta 2004; Pratinidhi 2010), stillbirth (Gupta 2006; Gupta 2012), maternal anaemia (Subramoney 2008), degenerative placental changes (Ashfaq 2008), and adverse infant neurobehavioural outcomes (Hurt 2005). Smoking more than one waterpipe per day (Tamim 2008) or starting to smoke waterpipes during the first trimester (Mirahmadizadeh 2008) was also associated with an increased risk of having a low birthweight baby.

Exposure to environmental tobacco smoke (ETS) also poses risks to pregnant women and their infants (Yang 2010). Studies suggest the risk may be exacerbated in low‐income countries where exposure to indoor cooking smoke is also common (Kadir 2010). In China, 75.1% of pregnant non‐smoking women were regularly exposed to environmental tobacco smoke from their husbands’ smoking (Yang 2010). Studies in high‐income countries demonstrate that eliminating smoking in the workplace and other public spaces significantly reduces environmental tobacco smoke exposure and improves health outcomes, including preterm births (Cox 2013). One study in Indonesia reported increased collective efficacy when environmental tobacco smoke exposure was addressed through a well‐publicised community household smoking ban (Nichter 2010). However, as these measures do not extend to homes (Oncken 2009), some argue domestic environmental tobacco smoke exposure may be increasing as public health policies restrict smoking of partners in public places, and the social position of women may limit their ability to enforce smoke‐free policies within their homes (Tong 2009).

A positive theme emerging from this literature is that a higher proportion of women stop smoking during pregnancy than at other times in their lives.  Up to 49% of women who smoked before pregnancy ‘spontaneously quit’ before their first antenatal visit (Quinn 1991; Woodby 1999; Hotham 2008), a quit rate substantially higher than reported in the general population (Ershoff 1999; McBride 2003; Tong 2008). However, these spontaneous quitting rates may be lower among women with lower socio‐economic status (Mullen 1999). There are significant psychosocial differences between women who 'spontaneously quit' and women who continue to smoke in late pregnancy. Women who spontaneously quit usually smoke less, are more likely to have stopped smoking before, have a non‐smoking partner, have more support and encouragement at home for quitting, are less seriously addicted, and have stronger beliefs about the dangers of smoking (Baric 1976; Ryan 1980; Cinciripini 2000; Passey 2012). Pregnant women are also more likely to use coping strategies to avoid relapse than non‐pregnant women (Ortendahl 2007c; Ortendahl 2008a; Ortendahl 2009a), however less than a third of these women remain abstinent after one year postpartum (CDCP 2002; Fang 2004), supporting qualitative evidence that many women see pregnancy as a temporary period of abstinence for the sake of the baby (Stotts 1996; Lawrence 2005a; Flemming 2013). Despite high relapse rates, some studies suggest that the long‐term effects of spontaneous quitting in pregnancy are significant (Rattan 2013), and others argue this success is important to recognise to avoid 'pathologising' smoking cessation and eroding confidence in human agency to overcome problems (Chapman 2010). 

Given the complexity of the health and social dimensions of smoking in pregnancy there are conflicting perspectives regarding the most appropriate approaches. A dominant theme is that smoking in pregnancy is a lifestyle choice, however, there is concern this can lead to 'victim blaming' (Bond 2005), that individualised, behaviourist approaches are unlikely to adequately address health inequalities alone (Baum 2009), and that drug dependence and addiction is best dealt with in the domain of social policy and public health (Ebert 2009). Nevertheless, some suggest there is a role for individual support which is positive, not punitive (Bond 2012), and others express a concern that framing smoking in pregnancy solely as a social problem may make health professionals reluctant to intervene and offer support (McLellan 2000).   

Other smoking cessation intervention reviews

At the time of this update there were 73 other Cochrane reviews assessing the effectiveness of tobacco smoking cessation interventions for all populations (see Appendix 1). These include reviews on the following.

• Population wide measures such as: legislative smoking bans, mass media campaigns, organisational interventions (workplace and school‐based interventions), healthcare financing systems for increasing use of tobacco dependence treatment, advertising and promotion to reduce tobacco use, preventing tobacco smoking in public places, and impact of advertising on adolescent smoking.

• Community interventions including family‐based programmes, group behaviour interventions, family and carer interventions for reducing environmental tobacco smoke, school‐based programmes, and school policies.

• Individual psychosocial interventions, including aversive smoking, acupuncture, hypnotherapy, self‐help, exercise, individual behavioural counselling, motivational interviewing, stage‐based interventions, competitions and incentives, telephone counselling, mobile phone‐based interventions, Internet‐based interventions, nursing and physician advice, enhancing partner support, feedback, community pharmacy interventions, training health professionals in smoking cessation, use of electronic records, prevention of weight gain after smoking cessation, improving recruitment into cessation programs, harm reduction, reduction versus abrupt cessation, biomedical risk assessments, electronic cigarettes, incentives to prevent smoking in young people, relapse prevention, and interventions to reduce non‐cigarette tobacco use, including waterpipe smoking cessation.

• Individual pharmacological interventions, including antidepressants, anxiolytics, nicotine replacement therapy (NRT), clonidine, mecamylamine, nicobrevin, nicotine agonists, opioid agonists, cannabinoid type 1 receptor agonists, silver acetate, lobeline, and nicotine vaccines, increasing adherence to medications for tobacco dependence, behavioural interventions as adjuncts to pharmacotherapies, combined pharmacotherapy and behavioural interventions;and an ‘overview of pharmacological reviews’.

•  Interventions in specific population groups, including people with: schizophrenia and serious mental illness, depression, substance abuse, cardiovascular and pulmonary disease; pre‐operative and hospitalised patients; Indigenous populations and Indigenous youth; and people in dental settings.

• Other reviews, assessing effectiveness of interventions to recruit patients into smoking cessation programs, and reduce harm from continued tobacco use.