Passive Smoking During Pregnancy and Early Childhood: Occurrence, Determinants, Health Effects and Prevention

Niina Jaakkola 7 ABSTRACT Although small children rarely smoke, tobacco smoke in their environment constitutes an extensive health hazard. The World Health Organization has estimated that, globally, almost half of all children are exposed to environmental tobacco smoke.Although small children rarely smoke, tobacco smoke in their environment constitutes an extensive health hazard. The World Health Organization has estimated that, globally, almost half of all children are exposed to environmental tobacco smoke. The general objective of this dissertation was to address public health issues related to prenatal and postnatal exposure to tobacco smoke products. The specific objectives were 1) to study the occurrence, trends, and determinants of smoking during pregnancy in Finland (Study I); 2) to study the occurrence and determinants of exposure to environmental tobacco smoke (ETS) during childhood in Finland (Study II); 3) to study the effects of exposure to ETS during pregnancy on fetal growth and length of pregnancy (Study III); and 4) to evaluate the effects of a populationbased smoking cessation program on smoking cessation and fetal exposure to tobacco smoke products (Study IV). These studies were all population-based representing geographically defined source populations. There were three population levels, nationwide, regional, and local. The nationwide study population consisted of 694,926 pregnant women in 1987-97 recorded in The Finnish Medical Birth Registry (Study I). On the local level, the source population consisted of all children in the city of Espoo born between 1.12. 1984 31.12. 1989 (Study II). The study population included a total of 2,568 children whose parents filled in the questionnaire (response rate 80.3%). The study focused on the 1,003 (39.1%) children whose one or both parents or guardians were current regular smokers. On the regional level, Studies III and IV were based on The Finnish Prenatal Environment and Health Study and included all the 2,751 children born 1.5. 1996 – 30.4. 1997 in two geographically defined hospital districts in South East Finland. Study III focused on 389 singleton newborns. In Study IV, the intervention group consisted of all women who were smokers at the time of their first visit to maternity health clinics and who gave birth in The Kymi Hospital District (306/1917). A reference group was chosen using identical inclusion criteria from The Porvoo Hospital District (152/834). Study I showed that smoking in pregnancy did not change in Finland between 1987 (15%) and 1997 (15%). Smoking was inversely related to age. It was more common in single than in married, and in occupations with low education requirements. The prevalence of smoking was Niina Jaakkola Abstract 8 highest in northern and eastern Finland and lowest in western Finland. The determinants of smoking remained similar, but the regional differences increased over the study period. Study II provided evidence that low education and single parenthood increases the risk of ETS exposure at home in children of smoking parents. The risk of exposure was found to be smaller for atopic children, and asthmatic children were not exposed at all. In Study III, the risk of preterm birth (<37 weeks) was increased in the presence of ETS exposure measured as hair nicotine concentration in non-smoking mothers after delivery. There was also an inverse linear relation between the mother’s hair nicotine concentration and the child’s mean birthweight. Study IV comprised a controlled evaluation of a smoking cessation intervention based on the training of maternity care nurses and providing them with health education material. The reference group received ordinary maternity care health education. The difference in quitting smoking during pregnancy between the intervention group and the reference group was 4.5% (95% CI −2.6 − 11.6%), indicating a small effect of intervention. The intervention group indicated that they received more information on the adverse effects of smoking, studied the material more actively, and felt that it influenced their smoking behavior more than the reference group did. There was no fference in the experience of receiving support for attempts to quit smoking between the two groups. In spite of increasing knowledge of its adverse effects, smoking during pregnancy has not declined in Finland over the past decade. The present results indicate that the resources of health education in the prevention of passive smoking should be focused on single parents and parents with a low educational background. Future smoking cessation programs need to offer more support to those attempting to quit. They should also emphasize the harmful effects on women’s own health as an additional reason for quitting. A task for the future is to find methods that are both effective and feasible to be used as a matter of routine maternity clinics. The effectiveness of these methods could be assessed in randomized controlled trials. However, the effectiveness and feasibility should also be evaluated in settings in which the influence of the evaluation itself is minimal. Original publications Niina Jaakkola 9 LIST OF ORIGINAL PUBLICATIONS This thesis is based on the following original publications referred to in the text by the Roman numerals I-IV. I. Jaakkola N, Jaakkola MS, Gissler M, Jaakkola JJK. Smoking during pregnancy in Finland: determinants and trends, 1987-1997. Am J Public Health 2001;91:284-286. II. Jaakkola N, Ruotsalainen R, Jaakkola JJK. What are the determinants of children’s exposure to environmental tobacco smoke at home? Scand J Soc Med 1994;21:107112. III. Jaakkola JJK, Jaakkola N, Zahlsen K. Fetal growth and length of gestation in relation to prenatal exposure to environmental tobacco smoke assessed by hair nicotine concentration. Environ Health Perspect 2001;109:557-561. IV. Jaakkola N, Zahlsen K, Jaakkola JJK. Effects of a population-based smoking cessation programme on smoking in pregnancy. Eur J Public Health 2001;11:446-449. The original publications are reproduced with the permission of the copyright holders. Niina Jaakkola Introduction 10