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Aboriginal mothers, breastfeeding and smoking

Aboriginal mothers, breastfeeding and smoking Dawn Gilchrist Goldfields South-East Health Region, Western Australia Abstract Objective: To document the smoking practices of Aboriginal mothers living in Perth during pregnancy and during the subsequent year while feeding their infants. Beth Woods Aboriginal community member, Western Australia Method: A cohort of mothers was followed Colin W. Binns School of Public Health, Curtin University of Technology, Western Australia from the time of delivery for 12 months to obtain details of infant feeding practices. A total of 455 mothers delivered between May 2000 and July 2001 and 425 completed the baseline questionnaire. Jane A. Scott Division of Developmental Medicine, University of Glasgow, United Kingdom Results: Prior to and during pregnancy, 67% of the mothers smoked regularly. While the rate appeared to decline slightly with the length of breastfeeding, the trend was not significant. The rate of smoking of Aboriginal mothers was significantly greater than for an earlier study of non-Aboriginal mothers in Perth, where the rate was Michael Gracey formerly Curtin University of Technology, Western Australia Hannah Smith obacco usage by mothers has a significant impact on the health of their children and on breastfeeding. Women of childbearing age who smoke expose their unborn foetus and then their children to the effects of passive smoking. With the decline in the number of men smoking, tobacco companies have increasingly diverted their efforts towards women and minority groups.1 In Australia, estimates from the 2001 National Drug Strategy Household Survey (NDSHS) show that about 3.1 million Australians (19.5% of people aged 14 years and over) smoke tobacco on a daily basis.2 The same survey estimated that 26% of the population are former smokers (30% of males and 23% of females) and 51% have never smoked (45% of males and 55% of females). In the 2001 NDSHS, almost half of the Aboriginal population surveyed reported that they smoked on a daily basis.2 A study of 200 Perth Aboriginal women found that almost half of the women surveyed were current smokers (49%), with 20.5% being ex-smokers and 30.5% had never smoked. This study revealed another use of tobacco in that 6% of the women reported having chewed tobacco at one time and just over half of these reported continuing to chew tobacco on a regular basis.3 Smoking is more prevalent in the lowest quintiles of socioeconomic disadvantage in the Australian population, which includes the Aboriginal population.4 As well as the effects of smoking on the health of adults, there has been extensive research on the effects of exposure of children to tobacco smoke. The 1992 US Environmental Protection Agency report detailed the link between exposure to passive smoking and increased incidence of lower respiratory infections, ear infection and asthma in infants and young children. Children exposed to tobacco smoke have reduced pulmonary function5 and during the first 18 months of life have increased rates of medical consultation and hospitalisation for respiratory illness.6 Mitchell and Milerad reviewed the 28.4%. Among Aboriginal women there was no difference in the percentage of smokers and non-smokers who initiated breastfeeding. While fewer women who smoked were still breastfeeding at 24 weeks postpartum, compared with nonsmokers (58% vs. 64%), this difference was not significant. Conclusions: The percentage of women smoking in this study is consistent with rates reported in the 2001 National Drug Strategy Household Survey. In other studies, smoking is associated with lower rates of breastfeeding initiation and duration, but this was not the case in the Aboriginal mothers. Implications: Although the high prevalence of smoking identified in this study did not appear to adversely affect breastfeeding, smoking during and after pregnancy does contribute to increased rates of low birth weight and other health problems in early childhood. Targeted antenatal smoking cessation programs are needed for Aboriginal mothers. (Aust N Z J Public Health 2004; 28: 225-8) Correspondence to: Professor C. W. Binns, Curtin University of Technology, School of Public Health, GPO Box U1987, Perth, Western Australia 6845. Fax: (08) 9266 2958; e-mail: cbinns@health.curtin.edu.au Submitted: August 2003 Revision requested: October 2003 Accepted: January 2004 2004 VOL. 28 NO. 3 AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH Gilchrist et al. Article association of maternal smoking and sudden infant death syndrome (SIDS). Their review of 50 studies identified a 4.7-fold increased risk of SIDS associated with smoking, after controlling for other risk factors such as sleeping position.7 However, it may be that prenatal exposure to smoke is more important than postnatal environmental exposure as a risk factor for SIDS.8 Data from the British National Child Development Study (NCDS) of a cohort of about 17,000, who were studied from age three to 33, was analysed to study the effect of maternal smoking. After adjusting for confounding factors there was an association between maternal smoking and diabetes (OR 4.55; 95% CI 1.82-11.36).9 A possible contributing factor to this association is to be found in a report of a study of 6,483 children in Germany.10 After controlling for many potential confounding factors, a dose-dependent association between overweight/obesity and maternal smoking during pregnancy was observed, suggesting that intrauterine exposure to inhaled smoke products, rather than lifestyle factors associated with maternal smoking, accounts for this finding.10 In addition to these direct risks to infant and child health, maternal smoking has been shown in numerous epidemiological studies to be negatively associated with both the initiation and duration of breastfeeding.11 In general, women who smoke are less likely to initiate breastfeeding12,13 and to breastfeed for shorter periods.13-15 Thus, the infants of mothers who smoke may be deprived of, or have reduced exposure to, the known health benefits of breastfeeding.16 In particular, the protection against respiratory infections conferred by breastfeeding when babies are exposed to smoke.17 The Perth Aboriginal Breastfeeding Study (PABS) was a longitudinal study undertaken to investigate the breastfeeding patterns of Aboriginal women who gave birth at Perth public hospitals. The questionnaires used included questions on past and present tobacco consumption, allowing the association of maternal smoking and breastfeeding to be studied. telephone interview at 2, 6, 10, 14, 18 and 24 weeks postpartum, or until they ceased to breastfeed. Those mothers agreeing to participate completed a self-administered baseline questionnaire while in hospital to determine breastfeeding initiation rates. The original PIFS baseline questionnaire was designed to identify feeding method while in hospital and to collect information on variables known, or suspected, to be associated with breastfeeding initiation and duration. The draft questionnaire was reviewed and modified by an adult literacy expert and then pilottested on a group of 20 new mothers. Further modifications were made based on their comments. The Aboriginal Nursing Staff at the Derbarl Yerrigan Health Service also assisted in reviewing the wording of the questionnaire for use in the PABS. Wherever possible the wording of the questionnaires was kept as close as practical to the PIFS version to allow for later comparisons. Data were computer coded, computer entered and analysed using the Statistical Package for the Social Sciences (SPSS for Windows, version 11). The Kaplan Meier statistic was used to investigate the dose-response relationship of cigarette smoking and breastfeeding duration. The data from the PABS were compared with data obtained from the PIFS. The National Health and Medical Research Council (NHMRC) principles of research in Aboriginal communities were followed.22 The project received approval from: the Human Research Ethics Committee of Curtin University, the Department of Health Western Australia (WA), Aboriginal Health Section, and the ethics committees of the participating hospitals. Results A total of 455 self-identified Aboriginal mothers gave birth during the study period and 425 women (93%) completed the baseline questionnaire. The main Perth maternity hospital contributed 310 mothers to the study, while five other hospitals provided another 115 mothers. At the first interview, while still in hospital, mothers were asked about their usual smoking habits, and these questions were repeated during the follow-up period. Follow-up proved to be very difficult and by the second interview at two weeks 162 women (38.1%) were lost. Of these, 101 women while giving birth in a Perth hospital gave a rural town as their permanent address and were no longer followed. A further 24 women were lost to followup during the course of the study and at six months only 239 of the 425 women who completed the baseline questionnaire remained in the study. The sample characteristics at birth and six months were compared and no significant differences were found in age, type of delivery, choice of initial feeding method, recent employment, educational level, and marital status. At discharge from hospital 89.4% of women were breastfeeding, declining to 55.8% at six months. There was no significant association between smoking and feeding method at discharge, and mothers who smoked (89.6%) were just as likely to be breastfeeding as non-smoking mothers (89.7%). The prevalence of maternal smoking at baseline is presented in Table 1. Throughout the duration of the study the percentage of 2004 VOL. 28 NO. 3 Methodology In this study, only mothers who identified themselves as Aboriginal were eligible to participate. In Western Australia, all persons who enter hospitals are asked if they identify themselves as Aboriginal. Many of the Perth public hospitals provide special support for Aboriginal clients and they make extra efforts to classify the ethnicity of their patients. All self-identified Aboriginal mothers who delivered in six Perth public hospitals between May 2000 and July 2001 were contacted and invited to participate in the study. The sample was consecutive and unselected. Mothers who agreed to participate in the PABS were interviewed in hospital and again at 2, 6, 10, 14, 18, 24 and 52 weeks post partum. The PABS used methodology very similar to the Perth Infant Feeding Study (PIFS) conducted from September 1992 to April 1993, the results of which have been published previously.18-21 A cohort of 556 Perth women delivering at two suburban public hospitals completed the questionnaire and were followed-up by AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH Indigenous Health Aboriginal mothers, breastfeeding and smoking Table 1: Smoking history at first interview of Aboriginal mothers and their partners living at home. Smoking history Never smokeda Smoking during pregnancy Smoked prior to Missing Total pregnancyb Table 2: Number of cigarettes smoked by breastfeeding mothers at two weeks and six months post discharge. Cigarettes smoked 1-10 11-20 21-30 31-40 41 or more Missing Total Mothers n % Partners % Mothers (PABS) Mothers (PABS) Mothers (PIFS) 2 weeks six months 2 weeks n % n % n % Notes: (a) For partners this includes never and ex-smokers. (b) Smoked prior to pregnancy and then stopped during pregnancy. Non-smokers 120 mothers smoking fell slightly with time. At six months the percentage of mothers smoking had fallen from 67% to 61%. Because of the risk of exposure to environmental tobacco smoke, it is important to know if any person is smoking in the household, not just the mother. Wherever possible, smoking information was obtained from 139 of the infants’ fathers living in the same house and of these 46% were smokers. There was a strong association between mothers and fathers both smoking (chi square 54.7, p<0.001). An additional six fathers smoked where the mother was not smoking, increasing the percentage of infants exposed to parental smoking to almost 70%. The details of the number of cigarettes smoked are shown in Table 2. Smoking prevalence was significantly related to age. Rates were 73.4% for mothers under 20 years, 68.8% for 20-30 years and 46.7% for those over 30 years of age (chi square 14.85, p<0.003). There was no adverse association between maternal smoking and duration of breastfeeding. While fewer mothers who smoked (58%) were still breastfeeding at 24 weeks compared with nonsmokers (64%), this difference was not statistically significant. Similarly, there was no significant dose-response relationship between the number of cigarettes smoked per day and breastfeeding duration (see Figure 1). At 24 weeks, 64% of nonsmokers were still breastfeeding compared with 55% of women who smoked 10 or fewer cigarettes a day, 62% of women who smoked between 11 and 20 cigarettes a day and 48% of women who smoked more than 20 cigarettes/day (Log rank χ2 =1.15 p=0.283). The high smoking rate observed in this study reflects the high rates of smoking in the general Aboriginal population. There was virtually no change in the prevalence of smoking by the Aboriginal mothers during pregnancy or while breastfeeding. Only 2.3% of Aboriginal mothers indicated that they had stopped smoking due to their pregnancy and while the proportion of Aboriginal mothers smoking declined with breastfeeding duration, this trend was not significant. A likely explanation for the decline in the number of smokers is that the mothers who breastfed for the longest were likely to be more health conscious and therefore likely to be non-smokers. This theory is supported by a review of studies investigating an association between maternal smoking and breastfeeding.11 In this review, studies of breastfeeding intention and initiation did not support an equal desire to breastfeed among smokers and non-smokers. We failed to find a negative association between smoking and either breastfeeding initiation or duration among Aboriginal mothers. While a larger proportion of non-smokers were still breastfeeding at six months compared with smokers, the doseresponse relationship between the number of cigarettes smoked each day and breastfeeding duration was neither significant nor consistent. For instance, a greater number of women who smoked Figure 1: Association between maternal smoking and breastfeeding duration. P roportio n of women breastfeeding Discussion A greater proportion of Aboriginal mothers in this study smoked compared with non-Aboriginal mothers in the PIFS (67% vs. 28.4%). These results are similar to those reported by Eades et al., who studied a cohort of Aboriginal mothers who delivered in the mid 1990s. They identified 515 mothers as eligible to enter the study and 53% participated in an interview at 6-12 weeks after delivery23 and the smoking prevalence was 65% (95% CI 59-71). The smoking ratio, quantity of cigarettes smoked, and breastfeeding rates of the earlier study are similar to the rates in the PABS.23 2004 VOL. 28 NO. 3 >20 cigarettes/day ≤ 10 cigarettes/day 11-20 cigarettes/day Non-smoker .4 0 4 8 12 16 20 24 Duratio n of bre astfeedi ng (wee ks) AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH Gilchrist et al. Article between 11 and 20 cigarettes a day were breastfeeding at six months than women who smoked 10 or fewer cigarettes per day. This finding is inconsistent with the majority of the recent literature, which suggests that women who smoke are less likely to breastfeed and to breastfeed for shorter periods than non-smokers.12-15 Amir and Donath11 conducted an extensive review of the epidemiological evidence that maternal smoking has a negative physiological effect on breastfeeding. While they identified several studies that found a dose-response relationship between the number of cigarettes smoked each day and breastfeeding initiation and duration that persisted after adjusting for confounding factors, they also identified a number of studies of population groups in which a high proportion of smokers breastfed successfully. They concluded that while a dose-response relationship between number of cigarettes smoked per day and the duration of breastfeeding may indicate a physiological effect of cigarette smoke on lactation, the effect could also be explained by psychological or behavioural differences between women who are light smokers and heavy smokers. Furthermore, a separate systematic review of possible physiological mechanisms that might explain the dose-response effect of smoking on lactation concluded that the evidence for a physiological mechanism was weak.24 There are some limitations that apply to the PABS. Aboriginal mothers were all self identified. Mothers who chose not to identify themselves as Aboriginal would not be included. We do not know how many women this would apply to; however, the participating hospitals make every attempt to identify and support Aboriginal mothers and it is unlikely that very many women would fall into the category. The follow-up rate at six months was 56% and this highlights the difficulties in following a population of Aboriginal women. Many of the women returned, or moved, to rural areas during the course of the study and could not be traced for follow-up. There were, however, no statistically significant differences found in the demographic characteristics between those followed up and those lost to the study, suggesting that the women who remained in the study were similar to those who were lost to follow-up. results of previous smaller studies. The implementation of culturally appropriate smoking cessation programs for Aboriginal populations, particularly before and during pregnancy and lactation, remains a high public health priority. Acknowledgements We gratefully acknowledge the willing assistance given by the mothers in our study, the hospital staff and community health workers. Without this assistance the study would not have been possible. The study was funded by a research grant from the National Health and Medical Research Council. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Australian and New Zealand Journal of Public Health Wiley

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References (29)

Publisher
Wiley
Copyright
Copyright © 2004 Wiley Subscription Services, Inc., A Wiley Company
ISSN
1326-0200
eISSN
1753-6405
DOI
10.1111/j.1467-842X.2004.tb00700.x
Publisher site
See Article on Publisher Site

Abstract

Dawn Gilchrist Goldfields South-East Health Region, Western Australia Abstract Objective: To document the smoking practices of Aboriginal mothers living in Perth during pregnancy and during the subsequent year while feeding their infants. Beth Woods Aboriginal community member, Western Australia Method: A cohort of mothers was followed Colin W. Binns School of Public Health, Curtin University of Technology, Western Australia from the time of delivery for 12 months to obtain details of infant feeding practices. A total of 455 mothers delivered between May 2000 and July 2001 and 425 completed the baseline questionnaire. Jane A. Scott Division of Developmental Medicine, University of Glasgow, United Kingdom Results: Prior to and during pregnancy, 67% of the mothers smoked regularly. While the rate appeared to decline slightly with the length of breastfeeding, the trend was not significant. The rate of smoking of Aboriginal mothers was significantly greater than for an earlier study of non-Aboriginal mothers in Perth, where the rate was Michael Gracey formerly Curtin University of Technology, Western Australia Hannah Smith obacco usage by mothers has a significant impact on the health of their children and on breastfeeding. Women of childbearing age who smoke expose their unborn foetus and then their children to the effects of passive smoking. With the decline in the number of men smoking, tobacco companies have increasingly diverted their efforts towards women and minority groups.1 In Australia, estimates from the 2001 National Drug Strategy Household Survey (NDSHS) show that about 3.1 million Australians (19.5% of people aged 14 years and over) smoke tobacco on a daily basis.2 The same survey estimated that 26% of the population are former smokers (30% of males and 23% of females) and 51% have never smoked (45% of males and 55% of females). In the 2001 NDSHS, almost half of the Aboriginal population surveyed reported that they smoked on a daily basis.2 A study of 200 Perth Aboriginal women found that almost half of the women surveyed were current smokers (49%), with 20.5% being ex-smokers and 30.5% had never smoked. This study revealed another use of tobacco in that 6% of the women reported having chewed tobacco at one time and just over half of these reported continuing to chew tobacco on a regular basis.3 Smoking is more prevalent in the lowest quintiles of socioeconomic disadvantage in the Australian population, which includes the Aboriginal population.4 As well as the effects of smoking on the health of adults, there has been extensive research on the effects of exposure of children to tobacco smoke. The 1992 US Environmental Protection Agency report detailed the link between exposure to passive smoking and increased incidence of lower respiratory infections, ear infection and asthma in infants and young children. Children exposed to tobacco smoke have reduced pulmonary function5 and during the first 18 months of life have increased rates of medical consultation and hospitalisation for respiratory illness.6 Mitchell and Milerad reviewed the 28.4%. Among Aboriginal women there was no difference in the percentage of smokers and non-smokers who initiated breastfeeding. While fewer women who smoked were still breastfeeding at 24 weeks postpartum, compared with nonsmokers (58% vs. 64%), this difference was not significant. Conclusions: The percentage of women smoking in this study is consistent with rates reported in the 2001 National Drug Strategy Household Survey. In other studies, smoking is associated with lower rates of breastfeeding initiation and duration, but this was not the case in the Aboriginal mothers. Implications: Although the high prevalence of smoking identified in this study did not appear to adversely affect breastfeeding, smoking during and after pregnancy does contribute to increased rates of low birth weight and other health problems in early childhood. Targeted antenatal smoking cessation programs are needed for Aboriginal mothers. (Aust N Z J Public Health 2004; 28: 225-8) Correspondence to: Professor C. W. Binns, Curtin University of Technology, School of Public Health, GPO Box U1987, Perth, Western Australia 6845. Fax: (08) 9266 2958; e-mail: cbinns@health.curtin.edu.au Submitted: August 2003 Revision requested: October 2003 Accepted: January 2004 2004 VOL. 28 NO. 3 AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH Gilchrist et al. Article association of maternal smoking and sudden infant death syndrome (SIDS). Their review of 50 studies identified a 4.7-fold increased risk of SIDS associated with smoking, after controlling for other risk factors such as sleeping position.7 However, it may be that prenatal exposure to smoke is more important than postnatal environmental exposure as a risk factor for SIDS.8 Data from the British National Child Development Study (NCDS) of a cohort of about 17,000, who were studied from age three to 33, was analysed to study the effect of maternal smoking. After adjusting for confounding factors there was an association between maternal smoking and diabetes (OR 4.55; 95% CI 1.82-11.36).9 A possible contributing factor to this association is to be found in a report of a study of 6,483 children in Germany.10 After controlling for many potential confounding factors, a dose-dependent association between overweight/obesity and maternal smoking during pregnancy was observed, suggesting that intrauterine exposure to inhaled smoke products, rather than lifestyle factors associated with maternal smoking, accounts for this finding.10 In addition to these direct risks to infant and child health, maternal smoking has been shown in numerous epidemiological studies to be negatively associated with both the initiation and duration of breastfeeding.11 In general, women who smoke are less likely to initiate breastfeeding12,13 and to breastfeed for shorter periods.13-15 Thus, the infants of mothers who smoke may be deprived of, or have reduced exposure to, the known health benefits of breastfeeding.16 In particular, the protection against respiratory infections conferred by breastfeeding when babies are exposed to smoke.17 The Perth Aboriginal Breastfeeding Study (PABS) was a longitudinal study undertaken to investigate the breastfeeding patterns of Aboriginal women who gave birth at Perth public hospitals. The questionnaires used included questions on past and present tobacco consumption, allowing the association of maternal smoking and breastfeeding to be studied. telephone interview at 2, 6, 10, 14, 18 and 24 weeks postpartum, or until they ceased to breastfeed. Those mothers agreeing to participate completed a self-administered baseline questionnaire while in hospital to determine breastfeeding initiation rates. The original PIFS baseline questionnaire was designed to identify feeding method while in hospital and to collect information on variables known, or suspected, to be associated with breastfeeding initiation and duration. The draft questionnaire was reviewed and modified by an adult literacy expert and then pilottested on a group of 20 new mothers. Further modifications were made based on their comments. The Aboriginal Nursing Staff at the Derbarl Yerrigan Health Service also assisted in reviewing the wording of the questionnaire for use in the PABS. Wherever possible the wording of the questionnaires was kept as close as practical to the PIFS version to allow for later comparisons. Data were computer coded, computer entered and analysed using the Statistical Package for the Social Sciences (SPSS for Windows, version 11). The Kaplan Meier statistic was used to investigate the dose-response relationship of cigarette smoking and breastfeeding duration. The data from the PABS were compared with data obtained from the PIFS. The National Health and Medical Research Council (NHMRC) principles of research in Aboriginal communities were followed.22 The project received approval from: the Human Research Ethics Committee of Curtin University, the Department of Health Western Australia (WA), Aboriginal Health Section, and the ethics committees of the participating hospitals. Results A total of 455 self-identified Aboriginal mothers gave birth during the study period and 425 women (93%) completed the baseline questionnaire. The main Perth maternity hospital contributed 310 mothers to the study, while five other hospitals provided another 115 mothers. At the first interview, while still in hospital, mothers were asked about their usual smoking habits, and these questions were repeated during the follow-up period. Follow-up proved to be very difficult and by the second interview at two weeks 162 women (38.1%) were lost. Of these, 101 women while giving birth in a Perth hospital gave a rural town as their permanent address and were no longer followed. A further 24 women were lost to followup during the course of the study and at six months only 239 of the 425 women who completed the baseline questionnaire remained in the study. The sample characteristics at birth and six months were compared and no significant differences were found in age, type of delivery, choice of initial feeding method, recent employment, educational level, and marital status. At discharge from hospital 89.4% of women were breastfeeding, declining to 55.8% at six months. There was no significant association between smoking and feeding method at discharge, and mothers who smoked (89.6%) were just as likely to be breastfeeding as non-smoking mothers (89.7%). The prevalence of maternal smoking at baseline is presented in Table 1. Throughout the duration of the study the percentage of 2004 VOL. 28 NO. 3 Methodology In this study, only mothers who identified themselves as Aboriginal were eligible to participate. In Western Australia, all persons who enter hospitals are asked if they identify themselves as Aboriginal. Many of the Perth public hospitals provide special support for Aboriginal clients and they make extra efforts to classify the ethnicity of their patients. All self-identified Aboriginal mothers who delivered in six Perth public hospitals between May 2000 and July 2001 were contacted and invited to participate in the study. The sample was consecutive and unselected. Mothers who agreed to participate in the PABS were interviewed in hospital and again at 2, 6, 10, 14, 18, 24 and 52 weeks post partum. The PABS used methodology very similar to the Perth Infant Feeding Study (PIFS) conducted from September 1992 to April 1993, the results of which have been published previously.18-21 A cohort of 556 Perth women delivering at two suburban public hospitals completed the questionnaire and were followed-up by AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH Indigenous Health Aboriginal mothers, breastfeeding and smoking Table 1: Smoking history at first interview of Aboriginal mothers and their partners living at home. Smoking history Never smokeda Smoking during pregnancy Smoked prior to Missing Total pregnancyb Table 2: Number of cigarettes smoked by breastfeeding mothers at two weeks and six months post discharge. Cigarettes smoked 1-10 11-20 21-30 31-40 41 or more Missing Total Mothers n % Partners % Mothers (PABS) Mothers (PABS) Mothers (PIFS) 2 weeks six months 2 weeks n % n % n % Notes: (a) For partners this includes never and ex-smokers. (b) Smoked prior to pregnancy and then stopped during pregnancy. Non-smokers 120 mothers smoking fell slightly with time. At six months the percentage of mothers smoking had fallen from 67% to 61%. Because of the risk of exposure to environmental tobacco smoke, it is important to know if any person is smoking in the household, not just the mother. Wherever possible, smoking information was obtained from 139 of the infants’ fathers living in the same house and of these 46% were smokers. There was a strong association between mothers and fathers both smoking (chi square 54.7, p<0.001). An additional six fathers smoked where the mother was not smoking, increasing the percentage of infants exposed to parental smoking to almost 70%. The details of the number of cigarettes smoked are shown in Table 2. Smoking prevalence was significantly related to age. Rates were 73.4% for mothers under 20 years, 68.8% for 20-30 years and 46.7% for those over 30 years of age (chi square 14.85, p<0.003). There was no adverse association between maternal smoking and duration of breastfeeding. While fewer mothers who smoked (58%) were still breastfeeding at 24 weeks compared with nonsmokers (64%), this difference was not statistically significant. Similarly, there was no significant dose-response relationship between the number of cigarettes smoked per day and breastfeeding duration (see Figure 1). At 24 weeks, 64% of nonsmokers were still breastfeeding compared with 55% of women who smoked 10 or fewer cigarettes a day, 62% of women who smoked between 11 and 20 cigarettes a day and 48% of women who smoked more than 20 cigarettes/day (Log rank χ2 =1.15 p=0.283). The high smoking rate observed in this study reflects the high rates of smoking in the general Aboriginal population. There was virtually no change in the prevalence of smoking by the Aboriginal mothers during pregnancy or while breastfeeding. Only 2.3% of Aboriginal mothers indicated that they had stopped smoking due to their pregnancy and while the proportion of Aboriginal mothers smoking declined with breastfeeding duration, this trend was not significant. A likely explanation for the decline in the number of smokers is that the mothers who breastfed for the longest were likely to be more health conscious and therefore likely to be non-smokers. This theory is supported by a review of studies investigating an association between maternal smoking and breastfeeding.11 In this review, studies of breastfeeding intention and initiation did not support an equal desire to breastfeed among smokers and non-smokers. We failed to find a negative association between smoking and either breastfeeding initiation or duration among Aboriginal mothers. While a larger proportion of non-smokers were still breastfeeding at six months compared with smokers, the doseresponse relationship between the number of cigarettes smoked each day and breastfeeding duration was neither significant nor consistent. For instance, a greater number of women who smoked Figure 1: Association between maternal smoking and breastfeeding duration. P roportio n of women breastfeeding Discussion A greater proportion of Aboriginal mothers in this study smoked compared with non-Aboriginal mothers in the PIFS (67% vs. 28.4%). These results are similar to those reported by Eades et al., who studied a cohort of Aboriginal mothers who delivered in the mid 1990s. They identified 515 mothers as eligible to enter the study and 53% participated in an interview at 6-12 weeks after delivery23 and the smoking prevalence was 65% (95% CI 59-71). The smoking ratio, quantity of cigarettes smoked, and breastfeeding rates of the earlier study are similar to the rates in the PABS.23 2004 VOL. 28 NO. 3 >20 cigarettes/day ≤ 10 cigarettes/day 11-20 cigarettes/day Non-smoker .4 0 4 8 12 16 20 24 Duratio n of bre astfeedi ng (wee ks) AUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH Gilchrist et al. Article between 11 and 20 cigarettes a day were breastfeeding at six months than women who smoked 10 or fewer cigarettes per day. This finding is inconsistent with the majority of the recent literature, which suggests that women who smoke are less likely to breastfeed and to breastfeed for shorter periods than non-smokers.12-15 Amir and Donath11 conducted an extensive review of the epidemiological evidence that maternal smoking has a negative physiological effect on breastfeeding. While they identified several studies that found a dose-response relationship between the number of cigarettes smoked each day and breastfeeding initiation and duration that persisted after adjusting for confounding factors, they also identified a number of studies of population groups in which a high proportion of smokers breastfed successfully. They concluded that while a dose-response relationship between number of cigarettes smoked per day and the duration of breastfeeding may indicate a physiological effect of cigarette smoke on lactation, the effect could also be explained by psychological or behavioural differences between women who are light smokers and heavy smokers. Furthermore, a separate systematic review of possible physiological mechanisms that might explain the dose-response effect of smoking on lactation concluded that the evidence for a physiological mechanism was weak.24 There are some limitations that apply to the PABS. Aboriginal mothers were all self identified. Mothers who chose not to identify themselves as Aboriginal would not be included. We do not know how many women this would apply to; however, the participating hospitals make every attempt to identify and support Aboriginal mothers and it is unlikely that very many women would fall into the category. The follow-up rate at six months was 56% and this highlights the difficulties in following a population of Aboriginal women. Many of the women returned, or moved, to rural areas during the course of the study and could not be traced for follow-up. There were, however, no statistically significant differences found in the demographic characteristics between those followed up and those lost to the study, suggesting that the women who remained in the study were similar to those who were lost to follow-up. results of previous smaller studies. The implementation of culturally appropriate smoking cessation programs for Aboriginal populations, particularly before and during pregnancy and lactation, remains a high public health priority. Acknowledgements We gratefully acknowledge the willing assistance given by the mothers in our study, the hospital staff and community health workers. Without this assistance the study would not have been possible. The study was funded by a research grant from the National Health and Medical Research Council.

Journal

Australian and New Zealand Journal of Public HealthWiley

Published: Jun 1, 2004

There are no references for this article.