Although the Department of Health recommends women avoid smoking in pregnancy, the most recent Irish data shows 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Our unpublished data from the Coombe Women and Infants University Hospital (CWIUH) shows that although there is a downward trend in maternal smoking since 2009, the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, pre-term birth (< 37 weeks gestation), placental abruption, pre-eclampsia and low birth weight of < 2,500g.^5,6,7 Pre-term birth is the leading cause of neonatal morbidity and mortality with a growing body of evidence suggesting a link between pre-term 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 postpartum 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%, pre-term birth by 7.8% and admissions to the neonatal intensive care unit (NICU) by 3.6%.¹⁹ Pre-term babies with a birth weight of 1,000-2,499g cost the healthcare system of Ireland up to approximately €2,450 per day to treat, depending on the level of care required by 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 have 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, most 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 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 to 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

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 5-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 2016-2026 plans to implement actions in the future to ensure all maternity hospitals/units will be tobacco-free and have an on-site 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 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.³⁸ 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 services. 

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 doctors 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, which 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, doctors 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

1. Coombe Women and Infants University Hospital (2014). Annual Clinical Report. HSE Print and Design: 2014
2. Shipton D, Tappin DM, Vadiveloo T et al. Reliability of self reported smoking status by pregnant women for estimating smoking prevalence: a retrospective, cross sectional study. BMJ 2009; 339:1-8
3. Dietz PM, Homa D, England LJ et al. Estimates of non-disclosure of cigarette smoking among pregnant and non-pregnant women of reproductive age in the United States. Am J Epid 2001; 173(3):355-359
4. Tong VT, Althabe F, Alemán A et al. Accuracy of self-reported smoking cessation during pregnancy. Acta Obstetricia et Gynecologica Scandinavica 2015; 94(1):106-111
5. Hammoud AO, Bujold E, Sorokin Y et al. Smoking in pregnancy revisited: findings from a large population-based study. Am J Obstet Gynecol 2005; 192(6):1856-1862
6. Salihu HM, Wilson RE. Epidemiology of prenatal smoking and perinatal outcomes. Early Human Development 2007; 83(11):713-720
7. Varner MW, Silver RM, Rowland Hogue CJ et al. Association between stillbirth and illicit drug use and smoking during pregnancy. Obstet Gynecol 2014; 123(1):113-125
8. Hammoud AO, Bujold E, Sorokin Y et al. Smoking in pregnancy revisited: findings from a large population-based study. Am J Obstet Gynecol 2005; 192(6): 1856-1862
9. Moster D, Lie RT, Markestad T. Long-term medical and social consequences of preterm birth. NEJM 2008; 359(3):262-273
10. Gluckman PD, Hanson MA, Cooper C, Thornburg KL. Effect of in utero and early-life conditions on adult health and disease. The NEJM 2008; 359(1):61-73
11. Reyes L, Manalich R. Long-term consequences of low birth weight. Kidney International 2005; 68(97):S107-S111
12. Bernstein IM, Mongeon JA, Badger GJ et al. Maternal smoking and its association with birth weight. Obstet Gynecol 2005; 106(5 Pt 1): 986-991
13. Gomez C, Berlin I, Marquis P, Delcroix M. Expired air carbon monoxide concentration in mothers and their spouses above 5ppm is associated with decreased fetal growth. Preventative Medicine 2005; 40(1):10-15
14. Li YF, Gilliland FD, Berhane K et al. Effects of in utero and environmental tobacco smoke exposure on lung function in boys and girls with and without asthma. Am J Respir Crit Care Med 2000; 162(6):2097-2104
15. Wisborg K, Kesmodel U, Henricksen TB et al. A prospective study of smoking during pregnancy and SIDS. Arch Dis Child 2000; 83(3):203-206 
16. Gilliland FD, Li YF, Peters JM. Effects of maternal smoking during pregnancy and environmental tobacco smoke on asthma and wheezing in children. Am J Respir Crit Care Med 2001; 163(2):429-436
17. Jones LL, Hassanien A, Cook DG et al. Parental smoking and the risk of middle ear disease in children: a systematic review and meta-analysis. Archives of Pediatrics and Adolescent Medicine 2012; 166(1):18-27
18. Murray RL, Britton J, Leonardi-Bee J. Second hand smoke exposure and the risk of invasive meningococcal disease in children: systematic review and meta-analysis. BMC Public Health, 2012; 12: 1062
19. Wong PP, Bauman A. How well does epidemiological evidence hold for the relationship between smoking and adverse obstetric outcomes in New South Wales? Austral New Zealand J Obstet  Gynaecol  1997; 37(2):168-173
20. European Foundation for the Care of Newborn Infants (EFCNI). 2011. EU Benchmarking Report 2009/2010 Too Little Too Late? Why Europe Should do More for Preterm Infants. Available from: http://www.efcni.org/fileadmin/Daten/Web/Brochures_Reports_Factsheets_Position_Papers/benchmarking_report/EFCNI_report_light_copyright.pdf (Accessed on Jan 28, 2016)
21. Mermelstein R, Lichtenstein E, McIntyre K. Partner support and relapse in smoking-cessation programs. J Consult Clin Psychol, 1983; 51(3):465-466
22. Berg CJ, Park ER, Chang Y, Rigotti NA. Is concern about post-cessation weight gain a barrier to smoking cessation among pregnant women? Nicotine and Tobacco Research 2008; 10(7):1159-1163
23. Lumely J, Chamberlain C, Dowswell T et al. Interventions for promoting smoking cessation during pregnancy. Cochrane Review 2009; 8(3):CD001055
24. Homish GG, Eidan RD, Leonard KE, Kozlowski LT. Social-environmental factors related to prenatal smoking. Addictive Behaviors 2012; 37(1):73-77
25. Ebert LM, Fahy K. Why do women continue to smoke in pregnancy? Women and Birth 2007; 20(4):161-168
26. Lanting CI, Buitendijk SE, Crone MR et al. Clustering of socioeconomic, behavioural, and neonatal risk factors for infant health in pregnant smokers. PLoS One 2009; 4(12):e8363
27. Ebert LM, Fahy K. ‘Why do women continue to smoke in pregnancy?’ Women and Birth 2007; 20(4):161-168
28. Roth LK, Taylor HS. Risks of smoking to reproductive health: assessment of women’s knowledge. Am J Obstet Gynecol 2001; 184(5):934-939
29. McCurry N, Thompson K, Parahoo K, O’Doherty E, Doherty A. Pregnant women’s perception of the implementation of smoking cessation advice. Health Education J 2002; 61(1):20-31
30. Lumely J, Chamberlain C, Dowswell T et al. Interventions for promoting smoking cessation during pregnancy. Cochrane Review 2009; 8(3):CD001055
31. Stead LF, Perera R, Bullen C et al. Nicotine replacement therapy for smoking cessation. Cochrane Database of Systematic Reviews 2012, 11
32. Kapur B, Hackman R, Selby P, Klein J, Koren G. Randomized, double-blind, placebo-controlled trial of nicotine replacement therapy in pregnancy. Current Therapeutic Research 2001; 62(4): 274-278
33. Slotkin TA. If nicotine is a developmental neurotoxicant in animal studies, dare we recommend nicotine replacement therapy in pregnant women and adolescents. Neurotoxicology and Teratology 2008; 30(1):1-19
34. Dempsey D, Jacob P, Benowitz NL. Accelerated metabolism of nicotine and cotinine in pregnant smokers.’ J Pharmacol Experimental Therapeutics 2002; 301(2):594-598
35. Dempsey DA, Benowitz NL. Risks and Benefits of Nicotine to Aid Smoking Cessation in Pregnancy. Drug Safety, 2001; 24(4):277-322
36. Cope GF, Nayyar P, Holder R. Feedback from a point of care test for nicotine intake to reduce smoking during pregnancy. Annals of Clinical Biochemistry 2003; 40(4):674-679
37. Quinn VP, Hollis JF, Smith K et al. Effectiveness of the 5-As Tobacco Cessation Treatments in Nine HMOs. J Gen Intern Med 2009; 24(2):149-154
38. National Maternity Strategy – Creating a Better Future Together 2016-2026, as accessed at http://www.health.gov.ie/publications
39. O’Higgins A, Murphy OC, Egan A et al. The use of digital media by women using the maternity services in a developed country. IMJ 2014; 107(10):313-315