Although the Department of Health recommends women to avoid smoking in pregnancy, the most recent Irish data show that approximately 11% of women continue to report this behaviour.¹ It is likely that this prevalence figure is an under-representation of the problem, as non-disclosure rates of 10-25% exist in self-reported smoking status in pregnancy.^2,3,4 Our unpublished data from the Coombe Hospital, Dublin shows that although there is a downward trend in maternal smoking since 2009, the proportions of heavy smokers have almost doubled.

Risks of smoking in pregnancy

Tobacco smoking during pregnancy is a key modifiable risk factor associated with a number of adverse outcomes including miscarriage, preterm birth (< 37 weeks gestation), placental abruption, pre-eclampsia and low birth weight of less than 2,500g.^5,6,7 Preterm birth is the leading cause of neonatal morbidity and mortality, with a growing body of evidence suggesting a link between preterm birth and long-term morbidities such as cerebral palsy and intellectual disability.^8,9

In addition to the 12-fold higher risk of mortality and the threefold higher risk of morbidity that low birth weight places on the early life of the infant, there are links to long-term health complications such as increased risk of coronary heart disease, type 2 diabetes and excess adiposity.^10,11 The topical area of ‘foetal programming’ is growing, whereby external factors present during pregnancy influence the intrauterine environment and are said to permanently affect future structure, physiology and metabolism, with smoking identified as a contributing factor. A dose-dependent and inverse relationship exists between smoking and foetal growth, such that even a reduction, as opposed to a complete cessation, in smoking in as late as the third trimester may improve this outcome.^12,13

Women must continue to be supported post-partum to maintain cigarette abstinence, as environmental smoke increases the risk of sudden infant death syndrome, asthma attacks, respiratory symptoms and illnesses, impaired lung function, middle ear disease and meningitis in children.^{14,15,16,17,18}

The cost of maternal smoking

Elimination of smoking in pregnancy has been estimated to prevent the incidence of low birth weight by 19.8%, preterm birth by 7.8% and admissions to the neonatal intensive care unit (NICU) by 3.6%.¹⁹ Preterm babies with a birth weight of between 1,000 and 2,499g cost the healthcare system of Ireland up to approximately €2,450 per day to treat depending on the level of care required for the infant.²⁰ Worryingly, these costs do not include the expenses incurred on the individual or the follow-up care costs after discharge from the NICU.

Why do pregnant women continue to smoke?

A multitude of reasons for continued maternal smoking and cessation relapse has been reported in literature, including lack of social support and post-cessation weight gain.^21,22 The most common associations with continuing to smoke in pregnancy are that of low socioeconomic status, having an unplanned pregnancy, having little or no social support, having a partner who smokes, and living with smokers.^23,24 These women experience greater and more severe stress than that of their more advantaged counterparts and smoking is perceived as a means of relief from anxiety and depression, making quitting more difficult.^25,26 For some women there is an increase in tobacco intake to cope with pregnancy-related pressures.²⁷ For many other women it is simply that they have not received any smoking cessation advice and are unaware of the risks smoking poses to pregnancy.^28,29 This education piece is perhaps the lowest hanging fruit that can be targeted by healthcare professionals in reducing the incidence of maternal smoking.

What can be done to help?

Financial incentives

Currently, maternal smoking cessation interventions are of high importance in research. A Cochrane review found that of all previously conducted interventions for smoking cessation in pregnant women, those that included a financial incentive to cease smoking were the most successful, mostly likely owing to the higher prevalence of tobacco smoking in people of a lower socioeconomic status.^27,30 Although financial incentives have one of the highest smoking cessation success rates, the translation of this type of intervention into primary care or maternity services is probably unrealistic.

Nicotine replacement therapy

In a meta-analysis of randomised controlled trials, nicotine replacement therapy (NRT) has been shown to increase the rate of smoking cessation by 50-70% in non-pregnant populations.³¹ The effectiveness of NRT in pregnancy however, has not demonstrated such positive results, with at least one trial showing no difference between the numbers of pregnant women who quit smoking with NRT compared to those without NRT.³²

Pharmacological interventions are lacking in the subject of pregnancy, most likely due to unknown effects on foetal development, as animal studies demonstrate that exposure to nicotine alone in the prenatal period disrupts brain development.³³ Moreover, there is debate over the doses and formulations of nicotine to be used in pregnancy due to significantly higher nicotine and cotinine clearance as well as a shorter half-life of cotinine.^34,35 Therefore, pregnant women are likely to require higher doses of nicotine than the general population to promote smoking cessation. This makes NRT a double-edged sword, as increases in NRT doses could in fact put the foetus at a similar risk as smoking itself. 

Counselling

The most feasible, safe and cost-effective of all smoking cessation interventions is that of brief counselling, which has been shown to improve cessations rates by 1-3% compared to unassisted quit attempts.³¹

Including feedback of nicotine metabolites such as carbon monoxide monitor readings within counselling has been shown to promote a two-fold increase in quit attempts.³⁶ As GPs are often the first to see the woman once she has become pregnant, they have the potential to play a vital role in educating women of the risks of smoking in pregnancy and it gives GPs the opportunity to support their patients throughout pregnancy and the postnatal period. 

In 2000, the US Public Health Service added an evidence-based smoking cessation intervention to its ‘Treating Tobacco Use and Dependence Clinical Practice Guideline’ called the 5-As. The five As encourage physicians to take around three minutes to:

• Ask patients about smoking at every visit

• Advise all tobacco users to quit

• Assess smokers’ willingness to try to quit

• Assist smokers’ efforts with treatment and referrals 

• Arrange follow-up contacts to support cessation efforts. When this framework is used correctly, the likelihood of smoking cessation is doubled.³⁷

Current strategies in Ireland

The National Maternity Strategy in Ireland 2016-2026³⁸ plans to implement actions in the future to ensure all maternity hospitals/units will be tobacco-free and have an onsite smoking cessation service available for pregnant women. 

Furthermore, midwives and other frontline healthcare professionals will have formalised and documented training in smoking cessation counselling. These actions, along with the continued support from GPs, have the potential to further decrease maternal smoking rates in Ireland. 

Our research in the UCD Centre for Human Reproduction in the Coombe Hospital is currently exploring whether online pregnancy-specific smoking cessation resources and social network support in combination with a counselling session may be more effective than current practice, given the high prevalence of internet use among pregnant women.³⁹ Should this be successful, it would prove a cost-and time-effective way to provide education and support to maternal smokers, which could be adopted by maternity and primary care settings alike.

Conclusion

Although recent overall trends in maternal smoking appear positive, there has been an increase in the number of heavy smokers, who are likely to need extra support in quitting. It is important that GPs take a few minutes to ask newly pregnant women about their smoking status and have resources available to educate women in this regard. 

Pregnancy has been described as a ‘teachable moment’ in a woman’s life, whereby it motivates women to spontaneously adopt healthier behaviours that, with appropriately timed assessment and intervention, could further promote abstinence of risky behaviours such as smoking. 

The bottom line is that in this influential time of a woman’s life, GPs have several opportunities at routine visits both pre-and antenatally to educate and support women to quit smoking and greatly influence the immediate and future health of both mother and child. 

References

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