Multimodal intervention raises smoking cessation rate during pregnancy
Abstract
Background. The aim was to study the effect of a multimodal smoking cessation intervention regimen on a number of pregnant smokers.
Methods. A prospective intervention study was designed where participants were allocated to intervention or control based on their birth date. The study included 647 pregnant smokers. The intervention group (n = 327) received initial individual smoking cessation counseling supplemented by an invitation to join, individually or in a group, a smoking cessation program with nicotine replacement therapy as a voluntary option. Intervention was designed as an integral part of the midwives' prenatal care. All pregnant smokers in the usual care group (n = 320) received standard counseling from a midwife. Outcome was self-reported smoking cessation in the 37th week of pregnancy and the reported cessation was validated by cotinine saliva concentration.
Results. Self-reported cessation rates during pregnancy were significantly higher in the intervention group (14%) than in the group receiving usual care (5.0%) (p < 0.0001) (Fisher's exact test). Cotinine-validated cessation rates during pregnancy were significantly higher among the former (7%) than the latter (2%) (p = 0.003). The adjusted odds ratio (OR) for smoking cessation was 4.20 (95% CI 2.13–8.03). Logistic regression analysis showed a significant positive association of smoking cessation with low caffeine consumption in pregnancy, many years in school, no exposure to passive smoking outside the home, and previous attempts to stop smoking.
Conclusions. A multimodal intervention regimen with initial individual counseling supplemented by an invitation to join a smoking cessation program with nicotine replacement therapy as a voluntary option markedly increased cessation rates during pregnancy.
Smoking during pregnancy carries a risk of lower birthweight and an increased risk of perinatal mortality (1,2). Quitting smoking, in turn, is associated with higher birthweight (3) and the number of stillbirths and infant deaths during a child's first year of life can be reduced if pregnant women stop smoking before the 16th week of pregnancy (4).
A meta-analysis of 11 randomized intervention studies demonstrated a 50% increase in quitting rates during pregnancy and that intervention in the form of several contacts, a variety of intervention modalities and follow-up are associated with higher quitting rates (5). The main components of these intervention programs were initial individual counseling by a specially trained care provider, self-help manuals supplemented by video or audiotape and other educational materials. Other reported initiatives are phone contacts, reinforced clinical support, mailed letters, homework and repeated individual counseling (5). A Norwegian study achieved a quitting rate of 38% by using smoking cessation groups for pregnant smokers (6). Use of nicotine replacement therapy has been shown to double the cessation rate among nonpregnant smokers (7,8). A review suggested that the benefits of such therapy in pregnant smokers outweigh the risk associated with continuous smoking (9). In 1995, 28% of all pregnant women in Denmark were smokers at the time of their first prenatal visit (National Board of Health, pers. commun., 2001). Although most Danish pregnant smokers were motivated for quitting smoking in a previous study, they seemed to need a helping hand (10). Almost all Danish pregnant women receive prenatal care at midwifery centers, where the woman is seen by the same midwife throughout her pregnancy.
In this study we tested an intensive regimen of intervention modalities shown to have a positive effect on smoking cessation in other studies (5–8). The intervention was integrated into the prenatal care at the midwifery centers.
The intervention included initial individual counseling supplemented by an invitation to join a smoking cessation program with nicotine replacement therapy as a voluntary option. The aim of our study was to evaluate the effect of this multimodal regimen on a number of pregnant smokers.
Materials and methods
This study is a prospective intervention study, which is part of the “Smoke-free Newborn Study.” The other parts of the “Smoke-free Newborn Study” were about passive smoking among nonsmokers and about maintaining the cessation of smoking among self-quitters in the very early pregnancy. Study approval was obtained from the local research ethics committee (journal no. KF-O2-084/95), and use of nicotine replacement therapy was authorized by the Danish Medicines Agency (registration no. 5312-149-1995).
All pregnant women paying their first prenatal visit to the Midwifery Center at a large university hospital during the period November 1996 to April 1998 were invited to join the Smoke-free Newborn Study. Exclusion criteria were: inability to speak Danish, age below 18 years, gestation of more than 22 weeks, verified psychiatric diseases, and alcohol or drug abuse.
Pregnant smokers born on uneven birth dates were summoned for prenatal consultation on weekdays where the center was staffed by midwives specially trained to counsel pregnant women on smoking cessation. These women formed the intervention group. Pregnant smokers born on even birth dates were summoned for consultation on weekdays where the center was staffed by midwives without such special training. These women formed the control group. The secretaries summoning the pregnant women were continuously reminded about this allocation criterion to avoid treatment diffusion between the intervention and the control group.
The first prenatal visit identified 905 pregnant women as daily smokers. The women were told that the study served the dual purpose of testing a new smoking cessation technique and collecting information about their daily habits. They were also told that intervention group participants would receive extra information about smoking cessation and would be invited to join a smoking cessation program, whereas control group participants would only receive information on usual prenatal care. Participation in the study required completion of two questionnaires and provision of two samples of saliva for cotinine measurement. All participants gave written informed consent, and the participants were then informed whether they belonged to the intervention or the control group.
The invitation was accepted by 696 (77%) of the 905 smokers eligible for participation, namely by 348 of 452 (77%) intervention group participants and by 347 of 453 (77%) control group participants.
The period between inclusion and the 37th week of pregnancy saw 10 participants having a miscarriage or stillbirth (intervention group: 5; control group: 5), 21 participants moving out of the area (intervention group: 9; control group: 12), and 17 participants having a premature delivery (intervention group: 7; control group: 10). These women were excluded and the study group eventually counted 647 women of whom 327 were in the intervention group and 320 in the control group.
The control group received usual care, which included routine information about the risk of smoking in pregnancy and general advice on smoking cessation or smoking reduction.
The intervention group received 1) individual counseling on smoking cessation by a specially trained midwife at the prenatal visit, 2) an invitation to join, individually or in a group, a smoking cessation program run by specially trained midwives, and 3) an offer of nicotine replacement therapy (Nicorette®, Pharmacia A/S, Denmark) as part of the program.
Individual counseling
Intervention was initiated immediately after study entry. The first visit was extended from the usual 30 min to 40 min and included a dialog about the woman's smoking habits and her motivation for smoking cessation during pregnancy. The invitation to join the smoking cessation program was given to all women who wanted to try to stop smoking. Participants received written information about the hazards of smoking in pregnancy and the risk of passive smoking for newborns and children. The subsequent 5–6 antenatal visits lasted 20 min, as usual. Pregnant women who had stopped smoking were encouraged to maintain this behavior.
Smoking cessation program
The smoking cessation program was based on a cognitive behavior modification program comprising self-reporting (daily cigarette consumption), stimulus control (delay in lighting up), response control (altered way of smoking) and reinforcement control, and maintenance strategies (cognitive coping, stress management).
A smoking cessation program was established with nine appointments (individually or in a group) over a period of 14 weeks. The first three attendances prepared the participants for quitting smoking. The six attendances after smoking cessation were used to maintain cessation and to hand out the nicotine substitution. Carbon monoxide expiration levels were measured at each meeting. Groups were chaired by two midwives and each meeting lasted 90 min. Individual smoking cessation sessions were chaired by one midwife and each meeting lasted 15–30 min.
Nicotine replacement therapy
Nicotine replacement therapy was offered in the form of 2 mg nicotine chewing gum or a 15 mg nicotine patch (16 h/day) or 2 mg nicotine chewing gum plus a 15 mg nicotine patch (16 h/day). The nicotine dosage was regulated according to Fagerström's test for nicotine dependence (11).
The nicotine substitution was maintained for a maximum of 11 weeks, and all women had stopped treatment before the 36th week of pregnancy. The specially trained midwives had attended a 5-day specialist training course focusing on adverse effects of smoking on pregnancy, smoking cessation techniques, nicotine replacement therapy and how to communicate with pregnant smokers.
The intervention regimen was tested in a pilot study over a period of 6 months. Pilot study participants filled in questionnaires about the intervention and some women participated in a telephone interview. Pilot study responses were used to adjust the multimodal intervention regimen.
Questionnaires/saliva cotinine samples
All study participants completed two questionnaires, the first after their first midwife visit, and the second before they visited the midwife in their 37th week of pregnancy. The questionnaires explored smoking habits, smoking history, previous smoking cessation attempts and knowledge about the hazards of smoking and attitudes to smoking, demographic data, alcohol intake, caffeine intake and psychosocial matters. The questionnaire in the 37th week of pregnancy also contained questions about the intervention process.
The first questionnaire was completed by 300 (92%) of 327 women in the intervention group and by 278 (87%) of 320 women in the control group (p = 0.03). The second questionnaire was completed by 270 (83%) of 327 women in the intervention group and 260 (81%) of 320 women in the control group; this difference was not significant (p = 0.7).
Women who did not complete the two questionnaires in due time were reminded to do so by phone or/and by mail. Eight percent had reminders for the first questionnaire, 20% for the second.
Saliva samples for cotinine measurement were collected at the first visit and in week 37 and analyzed by gas chromatography (12). Data from the first visit were available from 233 of 327 (71%) women in the intervention group and from 229 of 320 (72%) women in the control group (p = 0.05); data from the visit in week 37 were available from 161 of 327 (52%) women in the intervention group and from 159 of 320 (48%) in the control group (p = 0.5).
Outcome measures
One outcome measure was self-reported smoking cessation in the 37th week of pregnancy. Where no such information was available, the woman was categorized as a smoker. The other outcome measure was self-reported smoking cessation and a saliva cotinine of less than or equal to 30 ng/mL in week 37. A cotinine value of 30 ng/mL or less was used as cut-off (13,14). Where no information on self-reported smoking status was available or no cotinine value was obtained, women were defined as smokers. Furthermore, women who reported themselves to be nonsmokers were classified as smokers if their cotinine value was >30 ng/mL.
Statistics
The sample size chosen of the intervention study was based on two key assumptions: a 20% quitting rate among smokers in the intervention group between the first visit and the 37th week of pregnancy, and a 5% quitting rate among smokers in the control group in the period between the first visit and the 37th week.
With an 80% power requirement and a 5% significance level, this suggested a target sample of 1000 pregnant smokers, including a dropout rate of 8% due to moving to other areas, miscarriage and stillbirths.
The expectation of a 20% quitting rate among smokers in the intervention group was based on results from studies of nicotine substitution for nonpregnant smokers (7,8) and the results of a smoking cessation study for pregnant smokers where smoking cessation counseling was pursued in groups (6). Categorical data were analyzed using Fisher's exact test and continuous variables using Wilcoxon's two-sample test when comparing intervention and control groups at baseline. The proportion of women quitting smoking within each group was calculated using Fisher's exact test. Differences between birthweights were computed using Wilcoxon's two-sample test and the prevalence of low birthweight within groups was assessed using Fisher's exact test. Variables of a priori interest in self-reported smoking cessation were screened for association with response (cessation yes/no) by univariate logistic regression using a 5% significance level. Variables selected in this way were then used in a multivariate logistic regression model, and the effects of these variables were consequently adjusted. Mean values are presented with 1 standard deviation (SD) and odds ratio (OR) with a 95% confidence interval (CI). Values were considered statistically significant at p < 0.05.
Results
Table I shows the distribution of background variables, smoking habits and aspects of lifestyle factors among the 647 pregnant participants who answered the questionnaire upon their first visit to the midwife. There were no differences between the intervention group and the control group with respect to age, number of years in school, marital status, parity, prepregnancy body mass index (BMI), daily cigarette consumption at the time of the first visit to the midwife and before pregnancy, smoking history, and their partner's smoking habits, Fagerström score, exposure to passive smoking in the home, alcohol and caffeine intake, gestational week and saliva cotinine concentration. More women were exposed to passive smoking in the home in the intervention group (77%) than in the control group (67%) (p = 0.03). Participation in the intensive smoking cessation program was accepted by 87 (27%) of the 327 invited women. Eighty-one women accepted participation in a group and six women accepted an individual smoking cessation program. Seventy-one of 87 participants (82%) participated in three or more of a total of nine meetings in the smoking cessation program. Seventy-five (86%) of 87 women participating in the smoking cessation program were using nicotine substitution in the form of a 15 mg nicotine patch (16 h/day) or 2 mg nicotine chewing gum or a 15 mg nicotine patch (16 h/day) plus 2 mg nicotine chewing gum. The self-reported smoking cessation rate was 14.4% in the intervention group (n = 327) vs. 5.0% in the control group (n = 320) (p < 0.0001) (Table II). There were no differences between the control group and that fraction of the intervention group for which we had no data on smoking cessation in the 37th gestational week as regards background variables, smoking habits and aspects of lifestyle at their first visit.
| Control group | Intervention group | p-value | |
|---|---|---|---|
| (n = 327) | (n = 320) | ||
| Background characteristics | |||
| Maternal age (years) (mean ± SD) | 29 ± 4.7 | 29 ± 4.6 | 0.68 |
| 12 years or more in school (%) | 45 | 43 | 0.55 |
| Married or cohabitant (%) | 87 | 90 | 0.29 |
| Primiparous (%) | 52 | 53 | 0.87 |
| BMI before pregnancy (mean ± SD) | 23 ± 4.7 | 23 ± 3.9 | 0.67 |
| Smoking habits and lifestyle factors | |||
| Smoking consumption before pregnancy (cigarettes/day) (mean ± SD) | 18 ± 5.3 | 18 ± 5.8 | 0.54 |
| Smoking consumption (cigarettes/day) (%) | |||
| 1–9 cigarettes | 29 | 29 | |
| ≥ 10 cigarettes | 71 | 71 | 1.00 |
| Smoking consumption (cigarettes/day) (mean ± SD) | 11 ± 0.4.9 | 11 ± 5.3 | 0.54 |
| Have previously stopped smoking (%) | 37 | 40 | 0.44 |
| Total smoking (years) (mean ± SD) | 13 ± 4.8 | 13 ± 4.5 | 0.39 |
| Age when started smoking (years) (mean ± SD) | 16 ± 2.7 | 16 ± 2.6 | 1.00 |
| Fagerström score (mean ± SD)* | 3.1 ± 2.1 | 3.3 ± 2.7 | 0.26 |
| Exposed to passive smoking in the home (%) | 77 | 67 | 0.03 |
| Exposed to passive smoking outside the home (%) | 89 | 89 | 1.00 |
| Partner is daily smoker (%) | 70 | 63 | 0.10 |
| Alcohol consumption (drinks/week) (mean ± SD) | 0.62 | 0.57 | 0.75 |
| Caffeine consumption (mg/day) (mean ± SD) | 326 ± 251 | 346 ± 258 | 0.30 |
| Cotinine in saliva (ng/mL) (median) | 141 | 139 | 0.75 |
| Gestational week at first antenatal visit (mean ± SD) | 16 ± 2.7 | 16 ± 2.9 | 0.52 |
- Caffeine consumption was calculated from daily intake of coffee (one cup = 100 mg), tea, chocolate (one cup = 50 mg), and cola [one bottle (0.5 L) = 50 mg]. Alcohol intake was calculated from weekly intake of beer (one bottle = one drink) and wine (one glass = one drink) and liquor [one glass (2 cL) = one drink]
- * Fagerström score measures nicotine dependence: high scores indicate high dependence
| Intervention group (n = 327) | Control group (n = 320) | p-value | |||
|---|---|---|---|---|---|
| n | % | n | % | ||
| Self-reported smoking cessation | 47 | 14.4 | 16 | 5.0 | <0.0001 |
| Self-reported smoking cessation and saliva cotinine ≤ 30 ng/mL | 23 | 7.0 | 7 | 2.2 | 0.004 |
Saliva cotinine measurements
The smoking cessation rate based on self-reports in combination with saliva cotinine values ≤30 ng/mL was 7.0% in the intervention group and 2.2% in the control group (p = 0.004) (Table II).
There were no differences between the control group and the fraction of women for which we had no cotinine data in the 37th week of pregnancy in terms of background variables, smoking habits and aspects of lifestyle at their first visit.
We used logistic regression analysis to examine the influence of the baseline variables and intervention procedure on self-reported smoking status at the 37th week of pregnancy. The OR for smoking cessation was 4.14 (95% CI 2.13–8.0) in the intervention group (Table III). Furthermore, smoking cessation was associated with low caffeine consumption in pregnancy, many years in school, no exposure to passive smoking outside the home and previous attempts to stop smoking. The number of cigarettes smoked at baseline was not significantly associated with smoking cessation according to the logistic regression analysis (data not shown).
| Variable | OR | 95% CI | p-value |
|---|---|---|---|
| Intervention (intervention/control) | 4.14 | 2.13–8.03 | <0.0001 |
| Caffeine consumption (mg/day) | 0.998 | 0.997–1.000 | 0.03 |
| Previous attempts at smoking cessation (yes/no) | 2.68 | 1.49–4.81 | 0.001 |
| Exposed to passive smoking outside the home (no/yes) | 2.51 | 1.10–5.72 | 0.03 |
| Years in school (≥ 12/< 12) | 2.16 | 1.19–3.92 | 0.011 |
The average weight of a fetus born after the 37th week of gestation was 3401 g among women in the intervention group compare with 3433 g in the control group. The difference between the two groups was not statistically significant (p = 0.6). Nor was there any statistically significant difference (p = 0.70) between the proportion of fetuses weighing less than 2500 g in the intervention group (3.6%) and in the control group (3.0%).
Discussion
Our results indicate that a multimodal intervention regimen effectively increases smoking cessation during pregnancy. In our study group of 647 pregnant women, we achieved a self-reported quitting rate of 14.4% among interventions vs. 5.0% among controls. The cotinine-validated quitting rate was 7.0% in the intervention group and 2.2% in the control group (p = 0.004). The OR for smoking cessation was 4.14 (95% CI 2.13–8.0) in the intervention group.
For this study a quasi-randomized design was chosen. This was to ensure that the pregnant smokers in the intervention group received initial smoking cessation counseling by specially trained midwives and that the pregnant smokers in the control group received initial counseling be midwives without any special training. The present design suffers from the weakness that allocation was based on birth dates known to the midwives recruiting the subjects. This might accordingly have influenced the recruitment, in which case the study would suffer from a selection bias. However, the lack of significant differences between the control group and the intervention group in terms of known background variables, smoking habits and lifestyle factors during the first antenatal visit would seem to defy the existence of this risk.
The strengths of the study include absence of treatment diffusion as all participants in the intervention group were seen by specially trained midwives as opposed to participants in the control group who were all consulting midwives without such training. The study enjoys a second advantage which is that intervention and control group participants were seen at different week days and hence could not easily share information.
Saliva cotinine data from the 37th week of pregnancy were only available for 51% of the participants, which may be ascribed to the general busyness associated with pregnancy visits and to the failure to set aside the extra time it takes to collect the samples. Participants whose cotinine data were missing were classified as smokers, and our results may therefore underestimate the effect of intervention as quitting rates were based on these values.
Our results are in accordance with the results reported in a meta-analysis by Lumley et al. of 30 trials on a smoking cessation program for pregnant women, which showed a significant fall in smoking in the intervention groups compared with the control groups (OR = 0.51; 95% CI 0.45–0.58) and an absolute difference of 6.6% for those who continued to smoke (3).
Dolan-Mullen et al.'s meta-analysis of intensive interventions studies reported a 50% increase in quitting in the intervention groups compared with the control groups. Most of these studies offered initial individual counseling by trained persons, self-help manuals and follow-up (5). We obtained a higher increase in the smoking cessation rate; a success that may be based on the combination of initial smoking cessation counseling by a trained midwife, a smoking cessation program offering nine meetings, and the nicotine replacement therapy offered.
In our study prenatal smoking cessation was associated with many years in school, no exposure to passive smoking out of the home, low caffeine consumption in pregnancy, and previous attempts to stop smoking. Another Danish study has also reported that a low level of caffeine consumption is associated with a better quitting rate among pregnant women (15). In our study, women who were not exposed to passive smoking quit smoking more easily than women exposed to passive smoking outside their homes. We therefore have reason to believe that it will be easier for Danish pregnant women to quit smoking if they are not exposed to passive smoking in the work-place and in other public places. A non-Danish study has shown that women find it easier to quit smoking during pregnancy if there are no other smokers in the household (16).
We were surprised to learn that only 27% of the pregnant women accepted the invitation to participate in the smoking cessation program considering their knowledge of the harmful effects of smoking. Participation may have been low because it demands frequent attendance and commitment. Moreover, smoking cessation programs for pregnant women were not the order of the day at the time when this study was conducted.
In our study the pregnant smokers participated in group-based smoking cessation counseling. This has previously been reported in a Scandinavian study (6). However, other studies have met little success in establishing smoking cessation programs for groups of pregnant women (3).
A previous study of the effect of nicotine patch therapy on the smoking cessation rate showed no effect among pregnant women (17). We used nicotine chewing gum, nicotine patch therapy or combined nicotine gum and patch therapy, which was offered to 87 participants in the smoking cessation program. A majority of 75 (86%) of these 87 women chose nicotine replacement therapy, which shows that it is, indeed, a feasible therapeutic modality in smoking cessation programs run by health care professionals.
Our study has shown that a multimodal intervention regimen comprising initial individual counseling supplemented by an invitation to join a smoking cessation program offering nicotine replacement therapy is effective if the regimen is administered by trained midwives and is an integral part of the general prenatal care. Our method is easily implemented in other prenatal care schemes as intervention may be undertaken by the existing staff pending short, specialist training. It would be interesting to see future studies test intervention as part of prenatal care where nicotine replacement therapy is combined with counseling on smoking cessation as this approach is less time-consuming than the design adopted in the present study.
Acknowledgments
This study was supported by: The Ministry of Health (The National Health Fund for Research and Development) 1400/8-114-1995, 1400/8-237-1996, 1400/10-135-1997, 1400/ 23–1998; the City of Copenhagen Health and Care Administration, Copenhagen Healthy City; the Danish Lung Association; the Danish Cancer Society; and Pharmacia A/S.
