Rates of smoking in pregnancy among Aboriginal and Torres Strait Islander women are high,1-3 with 52% smoking during pregnancy compared with 15% in non-Indigenous Australian women.3,4 Smoking during pregnancy among Aboriginal women is inversely related to socioeconomic status,4 and in qualitative studies, Aboriginal women have nominated stress as a major reason for smoking.5,6 Indigenous women in other developed countries also have higher rates of smoking during pregnancy than women in the general population.7-9
As smoking rates in the general population have fallen in high-income countries, smoking has become more closely related to entrenched social disadvantage.10 A review of interventions for promoting smoking cessation during pregnancy10 showed that intervention was associated with a significant overall reduction in smoking during late pregnancy (risk ratio [RR], 0.94 [95% CI, 0.93–0.96]). The review suggested there was a need for studies to refine interventions to address the specific needs of disadvantaged subpopulations.10
Our study was conducted at three Aboriginal community-controlled health services located in urban communities in Queensland and Western Australia. Pregnant Aboriginal and Torres Strait Islander women who attended antenatal clinics at the participating health services were the target population.
Women were considered eligible to participate in the study if they were Aboriginal or Torres Strait Islanders; were attending their first antenatal appointment at one of the Aboriginal community-controlled health services at or before 20 weeks’ gestation; were aged 16 years or older, were self-reported current smokers or recent quitters (quitting when they knew they were pregnant); and were residents of the local area. Recent quitters were included because there is evidence that such women often relapse, either later in pregnancy or after the birth.11,12 Women were excluded if their pregnancy was complicated by a mental illness or they were receiving treatment for chemical dependencies other than tobacco or alcohol use.
A randomised controlled design was used. To reduce the probability of contamination by providers delivering the intervention to both the intervention group and the usual care group, and to increase the ease with which health care providers could follow the experimental protocol, randomisation was by week of clinic attendance. An Excel computer program was used to randomly allocate weeks to intervention or control for all clinics. At the beginning of each week, clinics were notified of the allocation sequence and the research assistant flagged the clinical record of study participants to indicate whether they were allocated to the usual care or intervention group. The person generating the allocation sequence was not involved in participant recruitment. Participants were informed of the purpose of the study at recruitment but not of their allocated treatment group until after they had provided consent.
The intervention was developed after a critical review of the literature and consultation with general practitioners, health care workers and community representatives in the health services.
For women in the intervention group, the intervention commenced at the woman’s first antenatal visit, with a scripted invitation from the doctor for her to quit smoking (details of script available from the authors on request). Women who agreed to stop smoking were then advised by the doctor to quit “cold turkey” and to return to the clinic staff again in 3–5 days, given the pernicious nature of smoking. The doctor also checked whether the woman had understood the advice, repeated any components not understood, and gave the woman an appointment reminder card for her wallet, a fridge magnet and a letter for other household members requesting they support the woman as she attempted to quit smoking. Women were asked to bring a partner or support person with them on their second visit. If women indicated at the first antenatal visit that they didn’t want to stop smoking, the doctor replied “I understand that it is difficult to stop smoking. However, because it is important, I would like to talk with you again about it when you next visit for antenatal care. Would that be OK?” Women could then indicate if they didn’t want to talk about smoking again at future antenatal visits.
To ensure adherence to the protocol during the study, a number of visits were made by the lead investigators, and intervention refresher training was provided.
Women in the usual care group received general advice from their GP about quitting smoking, based on existing brief intervention guidelines.13
Women were asked to provide the contact details of three people who would be able to contact them. The women were given a written appointment date and time for their next clinic visit. They were also phoned and sent text messages by mobile phone to remind them of each appointment.
Outcome assessments were conducted between 36 weeks’ gestation and delivery. Women who reported they had quit smoking were asked to provide a urine sample for cotinine analysis, and a portion of the sample was frozen at – 20°C before analysis.
A Cozart microplate ELISA (enzyme-linked immunosorbent assay) test kit (Concateno, London, UK) was used for urine analysis. All samples were analysed in duplicate, with final results based on the average result of two paired wells. A woman was defined at follow-up as being a current smoker if (i) she reported that she had smoked in the previous 7 days; (ii) she reported that she had not smoked within the previous 7 days, but had a urine cotinine level of ≥ 250 ng/mL at the time; or (iii) she did not provide a urine sample.5
Baseline characteristics of the two intervention groups are presented as frequency distributions for categorical variables and medians and quartiles for continuous variables. Because of the small numbers of quitters, exact logistic regression analyses were used to compare 36-week smoking status between the two groups after adjusting for recruitment centre. Relative risks and 95% confidence intervals were estimated using the Mantel–Haenszel technique, with stratification by health service.
We planned to recruit 270 smokers into the study over a 30-month period (135 women in each of the intervention and control groups). We assumed that 80% of women (108 per group) could be followed up. This sample size for outcomes would allow detection of a 20% difference between groups in smoking cessation (assuming a quit rate of 15% in the control group), with 5% significance level and 80% power, and allowing for a design effect of 1.5 for clustering of participants within clinics.
A flow diagram of randomisation and recruitment of trial participants is shown in Box 1. Of the 263 women who consented to participate, 148 were in the intervention group and 115 in the usual care group. Two-thirds of the women (176 [67%]) completed the outcome assessment: 98 (66%) in the intervention group and 78 (68%) in the usual care group.
Women in both groups were similar in terms of the median number of cigarettes smoked per day, number of weeks’ gestation at recruitment, and parity (Box 2). Compared with the usual care group, a slightly higher proportion of women in the intervention group were from Clinic 1, and a slightly lower proportion had a partner. The intervention group had a higher proportion of recent quitters than the control group. Consequently, we undertook a post-hoc subgroup analysis that included only those women classified as regular or occasional smokers at baseline.
In over 64% of intervention consultations, doctors adhered to the protocol in providing key components of the intervention. Lower proportions of nurses and health workers recorded that they had provided intervention advice (Box 3).
At 36-week follow-up, there was no significant difference in smoking rates between the two groups. Of the women followed up, 87 (89%) in the intervention group and 72 (95%) in the usual care group were smokers (RR for intervention versus usual care, 0.93 [95% CI, 0.86–1.08]; P = 0.212) (Box 4).
As expected, smoking rates were higher in the intention-to-treat analysis, with 137 smokers (93%) in the intervention group and 111 smokers (97%) in the usual care group (RR, 0.95 [95% CI, 0.90–1.01]; P = 0.207) (Box 4).
Subgroup analysis excluding baseline recent quitters showed no significant differences in smoking rates between the intervention group and the usual care group (P = 0.992) (Box 5). Corresponding figures for the intention-to-treat analysis were 123 smokers (99%) in the intervention group and 105 smokers (98%) in the usual care group (RR, 1.01 [95% CI, 0.98–1.04]; P = 0.965) (Box 5).
At 36-week follow-up, we found no significant difference in smoking rates between pregnant women who received a high-intensity quit-smoking intervention compared with those who received usual care. To our knowledge, ours are the first cotinine-validated quit rates reported for Aboriginal and Torres Strait Islander women in any intervention study.
In our study design we estimated that women who received the intervention would have a 20% higher absolute quit rate than women in the control group. We based this estimate on the high proportion of Aboriginal and Torres Strait Islander women who smoked during pregnancy compared with non-Indigenous pregnant women. We expected to find that a large number of women would have lower levels of nicotine dependence and would be able to quit with intensive support. A previous study of Aboriginal people had shown high levels of motivation to quit among pregnant women compared with other adults.14 However, our expectations were not borne out by our results.
At baseline, there were more recent quitters in the intervention group than the control group. Post-hoc analysis of the subgroup of women that excluded baseline quitters showed that smoking rates in the intervention and usual care groups were more similar at follow-up than at baseline. This suggests that most of the non-smokers at follow-up were those who were recent quitters at baseline. One possible reason for this is that, in this population, once women quit smoking in pregnancy they tend to remain quitters for the duration of the pregnancy. This is contrary to previous evidence that women who quit smoking when they become pregnant are likely to relapse later in the pregnancy.11,12
2 Baseline characteristics of participants in the intervention and usual care groups*
Median number of cigarettes smoked per day (interquartile range) |
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Median number of weeks’ gestation at recruitment (interquartile range) |
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3 Compliance of doctors and health workers/nurses with the intervention protocol*
Health worker’s or nurse’s compliance at first antenatal visit |
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4 Number (%) of women smoking at ≥ 36 weeks’ gestation, based on cotinine validation of self-report:* complete outcome versus intention-to-treat analysis
Received 8 July 2011, accepted 14 March 2012
Abstract
Objective: To determine the effectiveness of an intensive quit-smoking intervention on smoking rates at 36 weeks’ gestation among pregnant Aboriginal and Torres Strait Islander women.
Design: Randomised controlled trial.
Setting and participants: Pregnant Aboriginal and Torres Strait Islander women (n = 263) attending their first antenatal visit at one of three Aboriginal community-controlled health services between June 2005 and December 2009.
Intervention: A general practitioner and other health care workers delivered tailored advice and support to quit smoking to women at their first antenatal visit, using evidence-based communication skills and engaging the woman’s partner and other adults in supporting the quit attempts. Nicotine replacement therapy was offered after two failed attempts to quit. The control (“usual care”) group received advice to quit smoking and further support and advice by the GP at scheduled antenatal visits.
Main outcome measure: Self-reported smoking status (validated with a urine cotinine measurement) between 36 weeks’ gestation and delivery.
Results: Participants in the intervention group (n = 148) and usual care group (n = 115) were similar in baseline characteristics, except that there were more women who had recently quit smoking in the intervention group than the control group. At 36 weeks, there was no significant difference between smoking rates in the intervention group (89%) and the usual care group (95%) (risk ratio for smoking in the intervention group relative to usual care group, 0.93 [95% CI, 0.86–1.08]; P = 0.212). Smoking rates in the two groups remained similar when baseline recent quitters were excluded from the analysis.
Conclusion: An intensive quit-smoking intervention was no more effective than usual care in assisting pregnant Aboriginal and Torres Strait Islander women to quit smoking during pregnancy. Contamination of the intervention across groups, or the nature of the intervention itself, may have contributed to this result.
Trial registration: Australian New Zealand Clinical Trials Registry ACTRN12609000929202.