The Exposure of Nonsmoking and Smoking Mothers to Environmental Tobacco Smoke during Different Gestational Phases and Fetal Growth. (Children's Health Articles)
Dejmek, Jan, Solansky, Ivo, Podrazilova, Katerina, Sram, Radim J., Environmental Health Perspectives
We studied the impact of maternal exposure to environmental tobacco smoke (ETS) on birth weight (BW), low birth weight (LBW), and intrauterine growth retardation (IUGR) according to self-reported maternal smoking habits in a sample of 6,866 singleton births. We obtained data about parental characteristics and maternal active smoking (AS) and passive smoking at delivery via maternal questionnaires and medical records. We used three categories of smoking habits (nonsmokers and those who smoked 1-10 or >10 cigarettes per day) and defined ETS exposure as 5 cigarettes per day smoked by others in the mother's presence. We used multiple regression and logistic regression procedures with adjustment for many associated covariates. We observed a significant reduction of the mean BW in infants of AS mothers. This reduction was only marginal for mothers who stopped smoking after recognizing their pregnancy. ETS exposure in 1,797 of 5,507 nonsmoking mothers reduced the mean BW of their infants by 53 g [95% confidence interval (CI), 24-82 g]. ETS exposure also significantly reduced BW in babies of AS mothers by 92 g (CI, 21-113 g) compared with BW of ETS-nonexposed AS mothers. The adjusted odds ratio (AOR) of LBW for ETS-exposed AS mothers was two times the LBW risk of ETS-nonexposed AS mothers(2.02; CI, 1.11-3.67); the AOR of ETS-exposed nonsmoking mothers was 1.51 (CI, 1.02-2.26). The AOR of IUGR for this group did not differ from unity (1.08; CI, 0.82-1.43). However, ETS exposure increased the AOR of IUGR for AS mothers from 1.64 (CI, 1.06-2.53) to 2.13 (CI, 1.70-2.67); ETS exposure reduced the BW of infants of nonsmoking mothers and contributed to additional BW reduction in infants of AS mothers. ETS exposure increased the risk of LBW but not that of IUGR in babies of nonsmoking mothers. Key words: active smoking, birth Weight, environmental tobacco smoke, fetal growth, IUGR, low birth weight, passive smoking.
The exposure to environmental tobacco smoke (ETS), frequently referred to as passive smoking, is causally associated with a variety of health outcomes in nonsmokers (1-3). This applies not only to cardiovascular and respiratory illnesses, including lung cancer, but also to some adverse reproductive effects (4-7). Those most at risk from ETS exposure appear to be neonates, young children, and possibly the fetus (8). Study after study is finding that ETS exposure adversely affects fetal growth with an elevated risk of low birth weight (LBW) (9-13). The impact of passive smoking on other reproductive outcomes is less clear; an elevated risk of spontaneous abortion (14) and sudden infant death syndrome (15) as well as impaired female and male fertility (16, 17) have been observed in some epidemiologic studies.
ETS--a complex mixture containing many developmental toxicants (e.g., polycyclic aromatic hydrocarbons, lead, nicotine, cadmium)--is an important source of indoor air contaminants. Alone, each smoker is exposed to self-produced ETS; smokers tend to spend more time in a smoking milieu being exposed to ETS produced by others. This additional exposure may increase the adverse effects of active smoking.
We examined the influence of self-reported active and passive smoking on fetal growth in a retrospective epidemiologic study in the frame of a wider project named the Teplice Program (18). The design of the present study enabled us to evaluate the effects of ETS on the fetal growth of infants delivered by nonsmoking mothers as well as by mothers who smoked during the different gestational phases (AS mothers).
Materials and Methods
We designed the study as a retrospective population study with an interview at delivery. The background sample included all singleton live births occurring in the districts of Teplice and Prachatice (Czech Republic) from April 1994 through March 1999. We excluded mothers who gave incomplete information about smoking and restricted the sample to the mother's first delivery in the study period. …