[Smoking cessation and pregnancy]

To assess the effectiveness of smoking cessation programs implemented during pregnancy and to assess the impact of these programs on the health of the fetus and infant, on the mother and on the family.

Randomized and quasi-randomized controlled trials identified by the search strategy of the Cochrane Pregnancy and Childbirth Group, supplemented by the search strategy of the Cochrane Tobacco Group.

Trials in which programs to increase smoking cessation were implemented during pregnancy.

Data were abstracted according to predetermined criteria by two observers (S Oliver + J Lumley or E Waters + J Lumley). A total of 40 trials, conducted between 1975 and 1997, comprising over 9,000 women were identified and included in the review. An additional study provided data on over 3,000 women in a cluster-randomized trial. Interventions commonly included in these programs were: the provision of information on the risks of smoking to the fetus and infant and the benefits of quitting; recommendations to quit; feedback about the fetus; teaching cognitive-behavioural strategies for quitting smoking. There was substantial variation in the intensity of the intervention and the extent of reminders and reinforcement through pregnancy. Participants were healthy pregnant women and the usual setting was a hospital or community antenatal clinic. The principal outcome measure was continued smoking in late pregnancy. Eight trials provided some information on fetal outcomes: mean birthweight, low birthweight, preterm birth and perinatal mortality.

Pooled data from 30 trials revealed a significant reduction in the odds of continued smoking in late pregnancy in the intervention groups (odds ratio (OR) = 0.51, 95% confidence interval 0.45 to 0.58). This equates to an absolute difference in the proportion continuing to smoke of 6.6%. The findings were similar when analyses were restricted to the 17 trials with biochemical validated smoking cessation (OR = 0.49, 95% CI 0.42 to 0.58 and an absolute difference in continued smoking of 7.2%); to the 11 trials where the intervention intensity was high (OR = 0.50, 95% CI 0.42 to 0.59 and an absolute difference in continued smoking of 8.6%); and to the 12 trials with a high quality score for the intervention--rated on the theoretical basis, the intensity of the intervention, detailed description of the intervention, process evaluation, validated smoking cessation--(OR = 0.47, 95% CI 0.40 to 0.56 and an absolute difference in continued smoking of 8.9%). The six trials with validated smoking cessation, a high intensity intervention and a high quality score had a pooled OR = 0.47, 95% CI 0.38 to 0.57 and an absolute difference in continued smoking of 9.2%. The subset of trials with information on fetal outcome revealed a reduction in low birthweight (pooled OR = 0.80, 95% CI 0.67 to 0.97), a non-significant reduction in preterm birth (pooled OR = 0.82, 95% CI 0.66 to 1.01), and an increase in mean birthweight of 41 g (95% CI 16.6 to 65.5), but no differences in very low birthweight, stillbirths, neonatal deaths or total perinatal mortality. Three trials of smoking relapse prevention among women who had stopped smoking by the first antenatal visit had a pooled OR = 0.73, 95% CI 0.45 to 1.18, for smoking in late pregnancy, with an absolute difference of 5.5%. The single large cluster-randomized trial showed no evidence of a decrease in continued smoking: the adjusted OR for quitting smoking by late pregnancy was 1.0, 95% CI 0.69 to 1.6. There were no differences in adjusted mean birthweight in this trial by intervention or control clinic. Process evaluation identified some problems with the implementation of this trial.

Smoking cessation programs implemented in pregnancy increase smoking cessation, lead to a small increase in mean birthweight and a small reduction in low birthweight and preterm birth. (ABSTRACT TRUN