Other selleck compound studies have noted similar results with lower fetal biometry at 20�C24 weeks gestation (Hanke, Sobala, and Kalinka, 2004), higher risk for fetal death, preterm delivery, and low birth weight (Gray et al., 2010; Jaddoe et al., 2008). SHS exposure during pregnancy has also been associated with poorer respiratory health among infants over the first 6 months of life (Jedrychowski et al., 2007), and among children with asthma, higher exposure to SHS is associated with higher externalizing behavior problems in the early school years (Yolton et al., 2008). Thus, accurate identification of SHS exposure among pregnant women is an essential first step to preventing negative consequences for maternal and infant health. The study is guided by social�Cecological theory (e.g., Corbett, 2001; Ennett et al.

, 2010; Green, Richard, and Potvin, 1996; Stokols, 1996) suggesting that multiple domains of influence such as household/family, peers, and workplace may provide a context for maintenance of smoking through pregnancy. For example, contexts characterized by the absence of antismoking rules and policies and a high number of individuals who smoke and continue to smoke around the pregnant woman are likely to support the maintenance of smoking during pregnancy. Alternatively, these sources of influence may provide motivation for quitting if social network pressures inhibit access or opportunity and provide social pressures to quit smoking during pregnancy. Finally, this theory would suggest that it is important to consider multiple domains of influence to understand the social context of smoking.

Thus, identification of multiple sources of SHS exposure across several contexts is important for understanding the social ecology of pregnancy smoking and of quitting and maintaining quit status. There is no gold standard for self-report measurement of SHS exposure during pregnancy. Most studies of pregnant women measuring SHS exposure (SHS) use one single item measure of SHS exposure. The most common methods of measuring SHS exposure among pregnant women have been a single question about partner smoking status or the number of cigarettes smoked by the partner (see Windham, Eaton, and Hopkins, 1999, review). When studies of pregnant smokers have included other questions, they consist of either a question about number of smokers in the household or hours of exposure to SHS (Leonardi-Bee et al.

, 2008; Newman et al., 2010; Pogodina, Brunner Huber, Racine, and Platonova, 2009; Windham et al.). Few prospective studies of maternal cigarette smoking during pregnancy have examined ongoing SHS exposure using more than single indicator measures of SHS exposure, although studies of postnatal SHS exposure Cilengitide or lifetime SHS exposure have more comprehensive measures (e.g., Edwards, 2009; Rise and Lund, 2005).