Prepared by Susan E. Moner, MD, Spaulding Rehabilitation Hospital, Boston, Mass.
Objective
To make recommendations on interventions that will reduce or stop smoking
in pregnant women in Canada.
Burden of Suffering
Aside from increasing morbidity and mortality from cancers, cardiovascular
and pulmonary disease in the mother, smoking has been implicated in the
etiology of abruptio placenta, placenta previa, spontaneous abortion, premature
delivery, and stillbirth. Retarded fetal growth in the offspring
of smokers may be attributable to several factors, including the vasoconstricting
properties of nicotine, elevated fetal carboxyhemoglobin and catecholamine
levels, fetal tissue hypoxia, reduced delivery of nutritional elements
and elevation of heart rate and blood pressure. Retarded fetal growth
(about 18% of cases are caused by prenatal smoking) is a significant public
health concern because low birth weight is the most important single determinant
of neonatal and infant morbidity and mortality.
Options
Options include smoking cessation advice given by a physician or midwife
and supplemented by print information, feedback of laboratory values,
group counselling, and multicomponent programs. Nicotine replacement therapy
is not considered.
Outcomes
For the fetus, outcomes include intrauterine growth retardation, and
shortened gestation. For the infant, outcomes include low birth weight,
respiratory distress syndrome, sudden death syndrome, decreased physical
growth, other respiratory disorders such as asthma, and reduced cognitive
ability. For the mother, outcomes were shortened gestations, increased
mordibity, other diseases and disorders associated with smoking, recidivism,
and smoking cessation. Costs were assessed.
Evidence
MEDLINE searches were done for the years 1966 to 1993 using the key
words smoking; smoking cessation; tobacco; infant, low birth weight; infant,
small for gestational age; infant, newborn; birth weight; fetal growth
retardation; abnormalities; brain; development; brain growth; psychometrics;
child development; pregnancy; prenatal care; exposure; delayed effects;
longitudinal studies; and evaluation studies. Authors were also searched
in Science Citation Index, experts consulted, files of organizations searched,
and bibliographies of papers reviewed. Study results were synthesized in
table or graphic format only.
Values
The 13-member Task Force of experts in family medicine, geriatric medicine,
pediatrics, psychiatry and epidemiology used an evidence-based method for
evaluating the effectiveness of preventive health care interventions. Recommendations
were not based on cost-effectiveness of options. Patient preferences were
not discussed.
Background papers providing critical appraisal of the evidence and tentative recommendations prepared by the chapter author were pre-circulated to the members. Evidence for this topic was presented and deliberated upon in 1- to 2-day meetings, 2 to 3 times per year from January 1993 to June 1993. Consensus was reached on final recommendations.
Benefits, Harms, and Costs
25% to 40% of pregnant women stop smoking, at least for a short time,
without intervention. 4 RCTs assessed smoking cessation advice and although
design problems occurred, quit rates through to the end of the pregnancy
were 6% to 14% in the intervention group and 1% to 6% in the control groups.
A meta-analysis of 3 trials showed that the odds ratio (OR) for quitting
after advice was 0.39, 95% CI 0.21 to 0.75. Women who had their first child
and received advice to stop smoking had infants who weighed 68 g more than
women who did not receive advice; no differences were found for the weight
of infants of women who were multiparas.
Feedback of laboratory values was assessed in 3 trials and did not significantly change smoking rates. 4 trials of group counselling were done, with mixed results: 1 with low compliance and 1 with a strong control intervention did not show any differences, while 2 studies showed higher abstinence rates after intervention (14% vs 8% and 15% vs 5%).
6 trials (4 RCTs) showed that quit rates were increased by all behavioural strategy interventions, birth weighs increased, and fewer low and very low birth weight babies were born to women who had quit smoking. 1 meta-analysis found that personal advice supplemented by written materials reduced smoking during pregnancy (OR 0.30, 95% CI 0.23 to 0.38).
3 studies found smoking cessation interventions were cost effective when taking into account the cost of the intervention and hospital deliveries.
Most mothers who quit smoking during pregnancy had started again after 3 years (72%) and 91% of those who had not quit during pregnancy were still smoking.
Recommendations
Recommendation grade [A, B, C, D, E] and level of evidence
[I, II-1, II-2, II-3, III] are indicated after each recommendation. Citations
in support of individual recommendations are identified in the guideline
text.
Sponsors
The Canadian Task Force on Preventive Health
Care developed this guideline with funding from Health Canada.
Source Document
Moner S.E. Smoking and pregnancy. In: Canadian Task Force on the Periodic
Health Examination. Canadian
Guide to Clinical Preventive Health Care. Ottawa: Health Canada,
1994; 26-36.