Exposure to environmental and mainstream tobacco smoke and risk of spontaneous abortion

The authors examined the risk of spontaneous abortion from environmental tobacco smoke (ETS) exposure in a prospective study of over 5,000 women conducted in California during 1990-1991. Among nonsmokers, there was little association by hours of ETS exposure at home or work (adjusted odds ratio (OR) for any exposure = 1.01, 95% confidence interval (CI) 0.80-1.27), or by paternal smoking. However, the risks associated with ETS exposure were increased among nonsmokers who had moderate alcohol or heavy caffeine consumption. A moderate association with maternal smoking was observed (adjusted OR for > or = 5 cigarettes per day = 1.3, 95% CI 0.91-1.9).