Hoda Abdellatif BDS, MPH, DrPH
Smoking cessation interventions in pregnancy reduce the proportion of women who continue to smoke in late pregnancy, and also reduce the risk for low birth weight infants and preterm birth.
In women who are pregnant or are seeking pre-pregnancy counseling, are smoking cessation interventions effective on smoking behavior and perinatal health outcomes?
The authors of this fourth updated systematic review conducted comprehensive electronic and hand searches for relevant clinical trials conducted from 1974 to 2008. One reviewer abstracted the data per protocol. Another reviewer checked the abstracted data. The authors considered for inclusion only randomized control trials (RCTs) or quasi randomized clinical trials in which the primary intervention promoted smoking cessation during pregnancy Participants were pregnant women in any care setting or seeking a pre-pregnancy consultation. The authors investigated a wide range of outcome measures, including those that were smoking-related, birth-related and mother-related. The primary outcome measures were smoking cessation behavior and birth weight of newborns. The authors also conducted random effects meta-analyses were carried out. They also conducted subgroup analyses to assess the effect of risk of trial bias, intensity of the intervention (ranging from self-help to pharmacological agents) and main intervention strategy used.
This systematic review included 72 trials that provided data on smoking cessation intervention outcomes on more than 25,000 pregnant women. This update to the 2004 review identified eleven new RCTs from 2003 to 2008, including four new cluster RCTs. Overall, the meta-analysis demonstrated moderate, statistically significant results favoring the interventions. There was a significant reduction in risk of smoking in late pregnancy following interventions (risk ratio (RR) 0.94, 95 percent confidence interval (CI) 0.93 to 0.96), an absolute difference of six in 100 women who stopped smoking during pregnancy. However, there is significant heterogeneity in the combined data (I2 > 60 percent). In the trials with the lowest risk of bias, the interventions had less effect (RR 0.97, 95 percent CI 0.94 to 0.99), and lower heterogeneity (I2 = 36 percent). Eight trials of smoking relapse prevention (more than 1000 women) showed no statistically significant reduction in relapse. Smoking cessation interventions reduced risk for low birth weight (RR 0.83, 95 percent CI 0.73 to 0.95) and risk for preterm birth (RR 0.86, 95 percent CI 0.74 to 0.98), and there was a 53.91g (95 percent CI 10.44 g to 95.38 g) increase in mean birth weight.
Smoking cessation interventions in pregnancy reduce the proportion of women who continue to smoke in late pregnancy, and reduce the risk for low birth weight and preterm birth.
Source of Funding:
The Australian Commonwealth Department of Health and Ageing.
Importance and Context:
Tobacco is a major risk factor for six of the eight leading causes of death globally. Tobacco smoking also has been reported to have many long-term health impacts for women and their children, particularly in pregnancy. Studies of smoking cessation interventions are important to determine which interventions, if any, are most effective. Reviews that systematically compile and assess results of these studies could help policy makers, clinicians and patients make prudent decisions which could improve health outcomes for mothers and their babies.
Strengths and Weaknesses of the Systematic Review:
This is the fourth update of a Cochrane systematic review that is comprehensive and addresses relevant concepts including an extensive search and evaluation of the literature based on the stated inclusion and exclusion criteria. In this review, the method of data extraction is unclear and conflicting. For example, the abstract states that one reviewer was checked by a second reviewer, but the methods section states there were two reviewers. The authors provided a comprehensive list of all included studies, along with the baseline characteristics of the participants. They identified several outcomes of interest, including six categories of interventions and the intensity of each. The analyses on each outcome is conducted both with respect to the combined group of all interventions and by type/intensity of intervention. They thoroughly investigated potential biases from each included study. They also conducted analyses through subgrouping to evaluate the effects of potential biases. The authors evaluated heterogeneity from both a statistical and clinical perspective and used random effects meta-analyses to combine studies. However, they did not perform a sensitivity analysis or publication bias analyses.
Strengths and Weaknesses of the Evidence:
This review included a large number of high quality studies. A weakness of the evidence is the different effects of specific interventions and their intensities across the studies that were variable and could not be individually evaluated. Designs and quality of the studies varied, which yielded a wide range of quality scores. To account for this, their conclusions were evaluated by appropriate subgroup based on quality analyses. The authors addressed a wide range of outcomes, which is a strength.
Implications for Dental Practice:
The review makes clear that in general, smoking cessation interventions are effective in promoting smoking cessation in later pregnancy and also lowering the risk for low birth-weight and preterm birth. However, it does not make clear which types of interventions are most effective, or at what intensity the effect is achieved. Because of the wide variety of outcomes across studies, it is difficult to summarize the effects of specific interventions for promoting smoking cessation during pregnancy and to draw reasonable implications for dental practice.