It should be emphasized that current research expands the notion of an adverse intrauterine environment beyond the traditional, nutrient-poor environment first elucidated by Barker and colleagues in their analysis of infants from the Dutch Famine Birth Cohort. Adverse intrauterine conditions may also be the result of exposure to viruses, such as influenza, increased levels of stress during pregnancy, and, most important for this review, maternal cigarette smoking and secondhand (passive) smoke exposure during pregnancy. In this expanded view of adverse intrauterine conditions and resulting effects on the fetus, an exposure such as prenatal exposure to cigarette smoke may lead to a negative maternal forecast for the fetus. While prenatal smoke exposure certainly contributes to this adverse environment, evidence that maternal cigarette smoking during pregnancy is correlated with other potential contributors to adverse in utero environmental conditions can make causal attribution difficult (see Knopik et al., 2009 for a review). This is indeed supported by recent work from our own group and others suggesting that maternal smoking during pregnancy is correlated with many risk factors, such as lower levels of maternal
