Smoking Cessation During Pregnancy and Relapse After Childbirth in Canada

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1 OBSTETRICS Smoking Cessation During Pregnancy and Relapse After Childbirth in Canada Nicolas L. Gilbert, MSc, 1,2 Chantal R.M. Nelson, MPH, PhD, 1 Lorraine Greaves, PhD 3,4 1 Maternal and Infant Health Section, Public Health Agency of Canada, Ottawa ON 2 Département de médecine sociale et préventive, Université de Montréal, Montreal QC 3 British Columbia Centre of Excellence for Women s Health, Vancouver BC 4 School of Population and Public Health, University of British Columbia, Vancouver BC Abstract Objective: This analysis was undertaken to determine the rates and determinants of smoking cessation during pregnancy and smoking relapse after childbirth in Canada. Methods: We used data from the Maternity Experiences Survey, a cross-sectional study of mothers who gave birth to a singleton baby in Canada in A total of 1586 mothers who smoked occasionally or daily before pregnancy were included in the analysis. Results: The rate of smoking cessation during pregnancy was 53.0% (95% CI 50.3% to 55.7%). Higher pre-pregnancy smoking frequency, Inuit origin, being aged 35 years, lower education, not attending prenatal classes, lack of social support, stress before or during pregnancy, and living with a smoker were independently associated with higher risk of continued smoking, while First Nations (off-reserve) origin was associated with a lower risk. Among those who had quit smoking, 47.1% (95% CI 43.5% to 50.6%) relapsed postpartum. Living with a smoker, not having breastfed, and having stopped breastfeeding were independently associated with a higher risk of relapse. Conclusion: This study highlights the need to tailor smoking cessation and prevention interventions for some high-risk groups of women. Résumé Objectif : Cette analyse a été menée pour déterminer les taux et les déterminants de l arrêt tabagique pendant la grossesse et de la rechute post-partum au Canada. Méthodes : Nous avons utilisé les données de l Enquête sur l expérience de la maternité, soit une étude transversale sur des mères ayant accouché à la suite d une grossesse simple au Canada en En tout, mères ayant fumé occasionnellement ou quotidiennement avant la grossesse ont été incluses dans l analyse. Résultats : Le taux d arrêt tabagique pendant la grossesse était de 53,0 % (IC à 95 %, 50,3 % - 55,7 %). Une consommation de cigarettes plus élevée avant la grossesse, être d origine inuite, être âgée de 35 ans ou plus, être moins scolarisée, la non-participation à des cours prénataux, le manque de soutien social, le stress avant ou pendant la grossesse et la cohabitation avec un fumeur étaient associés de façon indépendante à un risque accru de poursuite du tabagisme, tandis que le fait d être issue des Premières Nations (hors-réserve) était associé à un risque moindre. Parmi les mères qui avaient cessé de fumer, 47,1 % (IC à 95 %, 43,5 % - 50,6 %) ont recommencé à fumer après l accouchement. La cohabitation avec un fumeur, ne pas avoir allaité et avoir cessé d allaiter étaient associés de façon indépendante à un risque accru de rechute. Conclusion : Cette étude souligne la nécessité d adapter les interventions d abandon et de prévention du tabagisme aux groupes de femmes exposées à des risques élevés. Key Words: Smoking cessation, smoking relapse, pregnancy Competing Interests: None declared. Received on May 26, 2014 Accepted on August 21, 2014 J Obstet Gynaecol Can 2015;37(1): JANUARY JOGC JANVIER 2015

2 Smoking Cessation During Pregnancy and Relapse After Childbirth in Canada INTRODUCTION Smoking during pregnancy is associated with increased risks of preterm birth, 1 3 intra-uterine growth restriction and low birth weight, 1,4 stillbirth, 5 and sudden infant death syndrome. 2,6,7 Smoking in pregnancy has declined steadily in Canada in recent years. The reported rate of women smoking during pregnancy fell from 21.8% (95% CI 20.5% to 23.1%) among women who gave birth between 1992 and 1996 to 12.3% (95% CI 11.2% to 13.5%) among those who gave birth between 2005 and Among Canadian women who gave birth in 2006, younger age (< 24 years), lower household income, living in rural areas, being born in Canada, and unwanted pregnancy, among other factors, were associated with a higher risk of smoking during pregnancy. 9,10 The Society of Obstetricians and Gynaecologists of Canada recommends that counselling be offered to pregnant women who smoke to help them quit smoking. 11 There is evidence that multi-component interventions, including aspects such as counselling, motivational interviews, and tailored information, are effective in decreasing the risk of continued smoking throughout pregnancy. 12 Women who do quit smoking during pregnancy are at high risk for relapse; approximately one half of women who quit during pregnancy relapse within one-year postpartum Social support, decreased self-efficacy, partner smoking, personal coping strategies, and stress have been documented as predictors of smoking relapse after delivery. 12 Little is known about the population-level determinants of smoking cessation and relapse from a national perspective. Such information may help to tailor and focus smoking cessation and interventions to prevent relapse. We undertook this analysis to determine the rates and determinants of smoking cessation during pregnancy and smoking relapse after childbirth in Canada. METHODS We used data from the Canadian Maternity Experiences Survey (MES) 9 for this analysis. The MES was a crosssectional survey conducted by the Public Health Agency of Canada (PHAC) and Statistics Canada of 6421 mothers aged 15 years or older who gave birth to a singleton baby in Canada in First Nations mothers living on reserve and institutionalized mothers were excluded. Participants were interviewed in 2006 or Interviews took place five to 14 months after the birth of their child, but were completed within nine months postpartum for 96.9% of participants. Women who participated in MES were asked about their smoking at three time points: 1. in the three months before pregnancy or before they realized they were pregnant; 2. during the last three months of their pregnancy; and 3. at the time of the survey. Stress before or during pregnancy was determined from the following question: Thinking about the amount of stress in your life during the 12 months before [baby s name] was born, would you say that most days were: not stressful, somewhat stressful or very stressful? Social support during pregnancy was determined from the following question: During your pregnancy, how often was support available to you when you needed it? (None of the time, a little of the time, some of the time, most of the time, or all of the time) Postpartum depression was determined using the Edinburgh Postnatal Depression Scale, 16 based on 11 questions about the mother s feelings. A total of 1586 MES participants smoked occasionally or daily before pregnancy or before they realized they were pregnant, yielding a weighted smoking rate of 22.0%. These women constituted the study sample. The MES was stratified by province or territory and by the woman s age. Smaller populations, the territories, and younger women (aged < 20 years) were oversampled. Each respondent was assigned a sampling weight calculated within weighting classes, which generally corresponded to the strata used to draw the sample. The 6421 MES respondents were thus weighted to represent women, which is considered a nationally representative sample. Data were analyzed using SAS 9.1 software (SAS Institute Inc., Cary, NC). Weighted rates of smoking cessation and relapse were calculated. Simple logistic regressions were used to estimate unadjusted odds ratios, and variables showing an association at P < 0.1 with the outcome were included in multiple logistic regression models to calculate adjusted odds ratios. Variables were retained in multiple regression models as long as their P value remained below 0.1. The variance and 95% confidence interval of rates and odds ratios were determined by bootstrap method using Bootvar, an SAS program developed by Statistics Canada. The MES was reviewed and approved by Health Canada s Research Ethics Board. JANUARY JOGC JANVIER

3 Obstetrics RESULTS The study sample consisted of 1586 women who smoked before pregnancy or before they realized they were pregnant, 810 women who quit smoking during pregnancy, and 416 who subsequently relapsed. The overall rate of smoking cessation during pregnancy was 53.0% (95% CI 50.3% to 55.7%) Higher pre-pregnancy smoking frequency, Inuit self-identification, higher parity, living in the territories, lower education, lower household income, unwanted pregnancy, not attending prenatal classes, lack of social support, stress before or during pregnancy, and living with a smoker were associated with a higher risk of continued smoking. In addition, women born outside North America and First Nations (off-reserve) women were significantly less likely to continue smoking. Finally, women aged 15 to 19 years, 20 to 24 years, and 35 years were at higher risk of continued smoking than those aged 30 to 34 years (Table 1). In multiple regression analyses, factors showing independent associations with the risk of continued smoking were higher pre-pregnancy smoking frequency, Inuit self-identification, being aged 35 years, lower education, not attending prenatal classes, lack of social support, stress before or during pregnancy, and living with a smoker. First Nations origin was associated with a lower risk of continued smoking (OR 0.48, 95% CI 0.26 to 0.88). Among women who had stopped smoking during their pregnancy, 47.1% (95% CI 43.5% to 50.6%) relapsed postpartum. Lower pre-pregnancy smoking frequency, younger age, living in the territories, lower education, lower household income, living with a smoker during pregnancy, not having breastfed or having stopped breastfeeding (compared with having continued to breastfeed), and being single were associated with a higher risk of relapse. The association between Aboriginal identity and relapse could not be assessed because of the small numbers of Métis and Inuit participants. There was no association between the time elapsed since childbirth (range 5 to 14 months) and the risk of relapse (Table 2). Among the above factors, those who reported living with a smoker and not having breastfed, or who had stopped breastfeeding, showed a significantly higher risk of relapse in multiple logistic regression analyses. In addition, women who had completed secondary school were at significantly higher risk for relapse than university graduates, although there was no dose response relation between education and smoking relapse. DISCUSSION The rate of smoking cessation by the last trimester of pregnancy in this study is slightly higher than the rate reported in the United States Pregnancy Risk Assessment Monitoring Survey (PRAMS), at 42.6%. 17 However, the rate of postpartum relapse in Canada is consistent with that measured by PRAMS in the United States. 13 As in previous studies, 18 we found that women who smoked a greater number of cigarettes pre-pregnancy were less likely to quit smoking during their pregnancy. One possible explanation is the strength of the addiction to nicotine. 19 Another potential explanation is that smoking is often used as a coping mechanism in dealing with stress, 20 as women in disadvantaged circumstances are less likely to consider quitting when other pressures (economic, social, and personal) are affecting their behaviours. 12 The association between younger age and higher cessation rates among smokers is noteworthy, as this pattern is different from the pattern of smoking rates during pregnancy: the MES showed that younger pregnant women were significantly more likely than their older counterparts to smoke during pregnancy, 9 but we found in the present study that they were also more likely to quit than those aged 35 and older. Previous studies suggest that younger pregnant women may be more inclined to quit smoking because the addiction to nicotine may be lower than older women, 21 or because of their shorter smoking histories, 12 or because they are more receptive to public health messages. However, the relapse rate of the younger age group post-pregnancy was much higher than that of their older counterparts, suggesting that their smoking cessation was only temporary. Alternatively, older women may be less sensitive to the social pressures to quit smoking than their younger counterparts. Inuit women had a higher risk of smoking throughout their pregnancy than non-aboriginal women, while off-reserve First Nations women had a lower risk. Some of these patterns are different from the rates of smoking throughout pregnancy: in the MES, the proportion of women smoking during the last trimester of pregnancy was 9.7% (95% CI 9.0% to 10.5%) in non-aboriginals 29.0% (95% CI 21.2% to 36.7%) in Métis, 62.6% (95% CI 50.4% to 74.7%) in Inuit, and 20.6% (95% CI 14.0% to 27.1%) in First Nations mothers (MES, unpublished data). There is a higher risk of relapse in the Territories (Yukon, Northwest Territories, and Nunavut); one possible explanation for this is the effect of a higher proportion of Inuit among the population. Consistent with public health literature, the rate of smoking cessation was lower in women who had lower levels of 34 JANUARY JOGC JANVIER 2015

4 Smoking Cessation During Pregnancy and Relapse After Childbirth in Canada Table 1. Determinants of smoking cessation during pregnancy in Canadian mothers Variable Smoking cessation among smokers, % (95% CI) Unadjusted odds ratio for continued smoking (95% CI) Adjusted odds ratio for continued smoking (95% CI) Smoking frequency Occasional 81.9 ( ) to 9 cigarettes/day 58.1 ( ) 3.27 ( ) 2.89 ( ) 10 to 19 cigarettes/day 36.7 ( ) 7.82 ( ) 6.36 ( ) 20 cigarettes/day 25.9 ( ) ( ) 9.59 ( ) Place of birth North America 51.7 ( ) 1.00 Outside North America 69.4 ( ) 0.47 ( ) Aboriginal self-identification First Nations 61.7 ( ) 0.72 ( ) 0.48 ( ) Inuit 13.1 ( )* 7.67 ( ) 4.38 ( ) Métis 39.3 ( ) 1.78 ( ) 1.08 ( ) Non-Aboriginal 53.6 ( ) Age, years 15 to ( ) 1.61 ( ) 1.13 ( ) 20 to ( ) 1.77 ( ) 1.20 ( ) 25 to ( ) 1.16 ( ) 1.07 ( ) 30 to ( ) ( ) 1.58 ( ) 2.04 ( ) Number of past live births ( ) ( ) 1.70 ( ) 1.52 ( ) ( ) 4.03 ( ) 3.18 ( ) Region of residence Atlantic 53.4 ( ) 1.32 ( ) 1.03 ( ) Quebec 52.4 ( ) 1.37 ( ) 1.62 ( ) Ontario 55.2 ( ) 1.23 ( ) 1.01 ( ) Prairies 47.5 ( ) 1.68 ( ) 1.42 ( ) British Columbia 60.2 ( ) Territories 29.0 ( ) 3.71 ( ) 1.25 ( ) Education Secondary, not completed 31.2 ( ) 6.46 ( ) 2.71 ( ) Secondary, completed 44.4 ( ) 3.67 ( ) 1.83 ( ) Post-secondary 57.0 ( ) 2.21 ( ) 1.29 ( ) University graduate 74.6 ( ) Household income, $ < ( ) 3.74 ( ) 2.36 ( ) to ( ) 3.55 ( ) 2.24 ( ) to ( ) 2.19 ( ) 1.76 ( ) ( ) Pregnancy wanted Sooner 57.4 ( ) 1.00 Later 51.7 ( ) 1.26 ( ) Then 55.9 ( ) 1.07 ( ) Not at all 36.5 ( ) 2.35 ( ) continued JANUARY JOGC JANVIER

5 Obstetrics Table 1. Continued Variable Smoking cessation among smokers, % (95% CI) Unadjusted odds ratio for continued smoking (95% CI) Adjusted odds ratio for continued smoking (95% CI) Timing of first prenatal visit, weeks < ( ) ( ) 1.47 ( ) Attended prenatal class Yes 67.5 ( ) No 46.4 ( ) 2.40 ( ) 1.49 ( ) Social support during pregnancy Never/little of the time 37.6 ( ) 1.97 ( ) Some of the time 45.0 ( ) 1.45 ( ) Most of the time 55.6 ( ) 0.95 ( ) All the time 54.2 ( ) 1.00 Somewhat/very stressed No 58.1 ( ) Yes 49.9 ( ) 1.39 ( ) 1.34 ( ) Depression before pregnancy No 54.3 ( ) 1.00 Yes 48.6 ( ) 1.26 ( ) Lived with a smoker No 69.3 ( ) Yes 38.8 ( ) 3.56 ( ) 2.62 ( ) Received information on tobacco, drugs, and alcohol during pregnancy Yes 53.3 ( ) 1.00 No 43.0 ( )* 1.51 ( ) *Coefficient of variation between 16.6% and 33.3% education and who had lower household incomes. These associations are attributed to a combination of mechanisms that include a lower uptake of prenatal care, a later initiation of prenatal care, smoking as a means of coping with difficult circumstances, and having a larger network of friends and family who are smokers than women with higher socioeconomic status. Research has shown that level of education is an especially important socioeconomic indicator, as it may reflect knowledge and skills that are important for making health behaviour choices, such as choosing to smoke. 22 Education level and occupational status, which usually reflect income levels, also link individuals to social structures and influence their access to material resources. 22 Limited material resources may explain why people smoke as a response to stress induced by unfavourable socioeconomic circumstances, as those who live in poorer socioeconomic circumstances often have more stresses (for example, living in unsafe neighbourhoods or unmet needs for food). Furthermore, better material resources may provide easier access to alternative ways of coping with disadvantage and stress than smoking, as their basic needs are met. 22 All participants in the MES had at least one prenatal care visit during their pregnancy. 9 However, having their first prenatal care visit earlier in pregnancy and attending prenatal classes were associated with higher rates of smoking cessation. Unfortunately, the MES did not document the actual interventions undertaken during prenatal care, so we do not know if the pregnant women who smoked received individual smoking cessation counselling as recommended by the SOGC. 11 However, the association between attending prenatal classes and smoking cessation remained significant after adjustment for the number of previous deliveries, indicating that it was not a result of confounding (e.g., from pregnant women being more likely to attend these classes in their first pregnancy). More research may be needed to determine how to use prenatal classes to more effectively reach pregnant women who smoke. Living with smoker(s) made it more difficult for pregnant women to quit smoking and increased the risk of relapse, a finding consistent with previous observations. 15 This finding was based on a question designed to assess 36 JANUARY JOGC JANVIER 2015

6 Smoking Cessation During Pregnancy and Relapse After Childbirth in Canada Table 2. Determinants of relapse after childbirth among Canadian mothers who had stopped smoking during their pregnancy Variable Relapse, % (95% CI) Unadjusted odds ratio for relapse (95% CI) Adjusted odds ratio for relapse (95% CI) Smoking frequency Occasional 40.0 ( ) to 9 cigarettes/day 57.0 ( ) 1.99 ( ) 10 to 19 cigarettes/day 50.8 ( ) 1.55 ( ) 20 cigarettes/day 44.9 ( ) 1.22 ( ) Place of birth North America 48.2 ( ) 1.00 Outside North America 37.3 ( ) 0.64 ( ) Aboriginal self-identification First Nations 58.4 ( ) 1.65 ( ) Inuit * Métis * Non-Aboriginal 45.9 ( ) 1.00 Age, years 15 to ( ) 3.04 ( ) 1.96 ( ) 20 to ( ) 1.40 ( ) 1.03 ( ) 25 to ( ) 1.14 ( ) to ( ) 1.01 ( ) 0.97 ( ) ( ) ( ) Number of past live births ( ) ( ) 1.22 ( ) ( ) 1.33 ( ) Region of residence Atlantic 51.2 ( ) 1.52 ( ) 1.03 ( ) Quebec 44.9 ( ) 1.18 ( ) 1.07 ( ) Ontario 48.6 ( ) 1.37 ( ) 1.09 ( ) Prairies 48.6 ( ) 1.37 ( ) 1.15 ( ) British Columbia 40.8 ( ) Territories 69.1 ( ) 3.24 ( ) 2.05 ( ) Education Secondary, not completed 58.0 ( ) 2.84 ( ) 1.54 ( ) Secondary, completed 58.4 ( ) 2.88 ( ) 1.94 ( ) Post-secondary 47.4 ( ) 1.85 ( ) 1.53 ( ) University graduate 32.8 ( ) 1.00 Family income, $ < ( ) 2.13 ( ) to ( ) 1.66 ( ) to ( ) 1.12 ( ) ( ) 1.00 Lived with a smoker during pregnancy No 41.2 ( ) Yes 56.3 ( ) 1.84 ( ) 1.48 ( ) continued JANUARY JOGC JANVIER

7 Obstetrics Table 2. Continued Variable Relapse, % (95% CI) Unadjusted odds ratio for relapse (95% CI) Adjusted odds ratio for relapse (95% CI) Age of baby at time of survey, months 5 to ( ) 1.19 ( ) 7 to ( ) 1.35 ( ) ( ) 1.00 Breastfeeding Did not breastfeed 69.5 ( ) 6.57 ( ) 5.60 ( ) Stopped breastfeeding 54.3 ( ) 3.43 ( ) 3.10 ( ) Still breastfeeding 25.7 ( ) Postpartum depression No 45.4 ( ) 1.00 At risk 51.2 ( ) 1.26 ( ) Yes 61.0 ( ) 1.88 ( ) Single No 45.6 ( ) 1.00 Yes 55.3 ( ) 1.48 ( ) *Unreliable estimates because denominator < 30 exposure to environmental tobacco smoke and did not distinguish the woman s partner from other household smokers. Nevertheless, by reinforcing the associations between smoke-free homes, exposure to tobacco smoke, and smoking cessation, this observation highlights the importance of targeting partners and family members in smoking cessation interventions for pregnant women; this aspect has been somewhat overlooked to date The lower risk of relapse among breastfeeding mothers is consistent with previous reports. 15,26 28 The duration of breastfeeding did not appear to influence this pattern. The data did not allow us to distinguish a direct effect of breastfeeding on smoking relapse (i.e., mothers do not relapse because they breastfeed) from the opposite (mothers stop breastfeeding because they resume smoking) or from an indirect association (e.g., some mothers are more likely to breastfeed and less likely to relapse because they are more eager to follow public health advice). However, previous qualitative research on women s smoking experience during pregnancy and postpartum indicated that breastfeeding is perceived as a reason not to resume smoking. 29 This study has a number of limitations. First, the exclusion of First Nations women living on reserves precludes any inferences for that population, as off-reserve First Nations women may be very different, at least with respect to socioeconomic conditions. Second, social desirability bias 30,31 may have led to an over-reporting of smoking cessation and an under-reporting of smoking relapse. However, the extent to which this may have biased the associations between smoking cessation, relapse, and other factors is unclear. Third, the survey was designed to examine various experiences in the pre-conception, prenatal, and postpartum period; therefore, the smoking data were limited, and we could not assess other facilitators or barriers to quitting and relapse such as smoking cessation interventions, heaviness of smoking, or other useful measures. CONCLUSION This study has confirmed that some sub-populations of pregnant women in Canada are at increased risk of continuing to smoke during pregnancy and/or may relapse after childbirth. The sub-populations include Inuit mothers, those of older age, those with lower education, and those living with a smoker. The study also highlighted some protective factors, such as attending prenatal classes and breastfeeding. These findings highlight the need to tailor smoking cessation and prevention interventions for some high-risk groups. ACKNOWLEDGEMENTS The authors are grateful to Jocelyn Rouleau and Juan Andrés León, from the Public Health Agency of Canada, for helpful advice. The MES was developed by the Maternal Experiences Study Group of the Public Health Agency of Canada s Canadian Perinatal Surveillance System (CPSS), and was administered by Statistics Canada. 38 JANUARY JOGC JANVIER 2015

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