Question
What are the effects of smoking cessation interventions during pregnancy on smoking behavior and perinatal health outcomes?
Relevance to nursing care
Tobacco smoking during pregnancy is a preventable factor associated with complications in pregnancy, stillbirth, low birth weight and preterm birth and has serious long-term implications for women and babies. Psychosocial interventions to support women to stop smoking during pregnancy can increase the proportion of women who stop smoking in late pregnancy and reducing low birth weight and preterm births.1
Study characteristics
This updated review included 86 randomized controlled trials (RCTs) conducted between 1976 and 2012. The studies included in the review were of mixed quality and there was a substantial level of heterogeneity amongst the trial results (I2 often greater than 50%). Seventy-seven RCTs involving over 29 000 women assessed as current or recent smokers were included in meta-analysis and results from nine trials were summarized in tabular form. Smoking status was defined variably between trials. Women from the 77 trials were generally healthy pregnant women aged more than 16 years. Two trials targeted women aged less than 20 years and one included women aged more than 15 years. Forty-seven trials included women of low socioeconomic status. Seven trials included a majority of women from ethnic minority groups including New Zealand Maori women and two trials recruited only aboriginal women (Aboriginal Australians and Alaskan Aboriginal women). Most trials recruited women at the first antenatal clinic visit and during the second trimester, excluding women in the last trimester.
The main interventions were categorized as counseling (n = 48), social support (n = 10) health education (n = 7), feedback (n = 7), and incentives (n = 4). Interventions varied considerably in intensity, duration, and people involved in delivery. Thirty-one trials had a single intervention and 33 trials had multiple interventions with different components offered to all women. Twelve trials had 'tailored' interventions based upon women's individual needs. Most counseling interventions were delivered face-to-face using either counseling alone or with motivational interviewing or cognitive behavioral therapy components.
Incentive-based interventions had the largest effect size compared with less intensive interventions (one study; RR 3.64, 95% CI 1.84 to 7.23) and an alternative intervention (one study; RR 4.05, 95% CI 1.48 to 11.11). Feedback interventions demonstrated a significant effect only when compared with usual care and provided in conjunction with other strategies, such as counseling (two studies; average RR 4.39, 95% CI 1.89 to 10.21), but the effect was unclear when compared with a less intensive intervention (two studies; average RR 1.19, 95% CI 0.45 to 3.12). The effect of health education was unclear when compared with usual care (three studies; average RR 1.51, 95% CI 0.64 to 3.59) or less intensive interventions (two studies; average RR 1.50, 95% CI 0.97 to 2.31). Social support interventions appeared effective when provided by peers (five studies; average RR 1.49, 95% CI 1.01 to 2.19), but the effect was unclear in a single trial of support provided by partners.
The effects were mixed where the smoking interventions were provided as part of broader interventions to improve maternal health.
The primary outcome of the review was smoking abstinence in late pregnancy, either self-reported or biochemically validated. Sixty RCTs and 10 cluster-randomized trials reported on this up to and including the period of hospitalization for birth (21 948 women).
In terms of the primary outcome, counseling interventions demonstrated a significant effect in comparison with usual care (27 studies; average RR 1.44, 95% CI 1.19 to 1.75, I2 = 55%). However, a significant effect was only present where counseling was provided with other strategies (11 studies; average RR 1.59, 95% CI 1.15 to 2.21, I2 = 45%), or tailored to the needs of individual women (six studies; average RR 1.49, 95% CI 1.01 to 2.20, I2 = 75%), but the effect was unclear when counseling was provided as a single intervention (10 studies; average RR 1.12, 95% CI 0.89 to 1.42, I2 = 11%).
Twelve secondary outcomes were specified in this review. Only the main results can be reported here. For smoking relapse prevention, the largest comparison (between studies comparing counseling and usual care), it was unclear whether interventions prevented smoking relapse among women who had stopped smoking spontaneously in early pregnancy (eight studies; average RR 1.06, 95% CI 0.93 to 1.21). However, an apparent effect was seen in smoking abstinence at 0-5 months postpartum (10 studies; average RR 1.76, 95% CI 1.05 to 2.95, I2 = 83%), a marginal effect at 7-11 months (six studies; average RR 1.33, 95% CI 1.00 to 1.77) and a significant effect at 12-17 months (two studies, average RR 2.20, 95% CI 1.23 to 3.96), but not in the longer term. In other comparisons for secondary outcomes, for example smoking reduction, the effect was not significantly different from the null effect for most secondary outcomes, but sample sizes were small.
Pooled effects were similar among interventions provided for women with generally low socioeconomic status (44 studies; average RR 1.41, 95% CI 1.19 to 1.66), compared with other women (26 studies; average RR 1.47, 95% CI 1.21 to 1.79), although the effect was unclear in interventions among women from ethnic minority groups (five studies; average RR 1.08, 95% CI 0.83 to 1.40) and aboriginal women (two studies; average RR 0.40, 95% CI 0.06 to 2.67). Notably, pooled results demonstrated that women who received psychosocial interventions had an 18% reduction in preterm births (14 studies; average RR 0.82, 95% CI 0.70 to 0.96) and infants born with low birth weight (14 studies; average RR 0.82, 95% CI 0.71 to 0.94). No adverse effects were reported from the included interventions and three studies showed improvements in women's psychological wellbeing.
Implications for nursing care
Psychosocial interventions to support women to stop smoking in pregnancy can increase the proportion of women who stop smoking during late pregnancy, reducing low birth weight and preterm births. Interventions seemed to be equally effective for women who were poor, as those who were not; but there was insufficient evidence that the interventions were effective for women from ethnic minorities and aboriginal women. Interventions delivered as part of routine pregnancy care did not appear to help more women to quit, suggesting challenges for translating evidence into practice.
Implications for research
The review offers numerous implications for research. Broadly, future research could establish which interventions are effective, how they work, who for and how they should be implemented, disseminated and institutionalized.
Acknowledgement
M.D.J.P. is a member of the Cochrane Nursing Care Field (CNCF).
Reference