We now move beyond the example of famine to consider one of the most common, potentially hazardous environmental exposures during pregnancy -- maternal cigarette smoking. Studies have shown that there are more than 4,000 chemicals in cigarette smoke including benzo(a)pyrene, nicotine, and carbon monoxide, and more than 40 of these chemicals are known carcinogens (Thielen, Klus, & Muller, 2008; US Department of Health and Human Services, 2010). Nicotine crosses the placenta, and fetal concentrations of nicotine can be 15% higher than maternal concentrations (Lambers & Clark, 1996). Despite a number of studies showing a decrease in the overall prevalence of smoking in women in the past 20 years, key studies have suggested that the prevalence of smoking in young pregnant women under 20 years of age has increased, with prevalence rates of 30–40 percent (Jaakkola, Jaakkola, Gissler, & Jaakkola, 2001; Mohsin & Bauman, 2005; “Smoking during pregnancy--United States, 1990–2002,” 2004). Others have reported that 12–15% of all women of childbearing age smoke while pregnant (Cnattingius, 2004; Goodwin, Keyes, & Simuro, 2007). Considering the fact that women who smoke during pregnancy
