Continued SHS exposure through pregnancy may also serve to reduce any initial motivation to quit smoking during pregnancy and selleck kinase inhibitor maintain women’s own smoking by lowering motivation to quit. Recent studies have demonstrated that motivation to quit is dynamic, with frequent fluctuations (West and Sohal, 2006), and lack of motivation to quit or declines in motivation predict relapse prospectively (McBride, Pirie, and Curry, 1992; Shiffman, Paty, Gnys, Kassel, and Hickcox, 1996). These results speak to the need to focus on sources of SHS exposure in smoking cessation interventions for pregnant women (Mullen, 2004) and offer cessation interventions to sources of SHS exposure in the women’s lives. This study has several limitations. First is the issue of restricted sample size for examination of changes in SHS exposure, as noted above.

Second, the results may only be generalizable to primarily lower socioeconomic status (SES) smokers with high school or below high school education. It is possible that sources and frequency of SHS exposure through pregnancy differ for higher SES women with different demographic characteristics. However, it should be noted that smoking during pregnancy is more common among younger, lower income women with less education (Gilman, Abrams, and Buka, 2003), suggesting that this may be a particularly important population with respect to pregnancy smoking. Another limitation is that the initial set of 42 oral fluid samples were assayed using ELISA, a less sensitive assay for cotinine. Thus, it is possible that of these 42 women, some were active smokers and were misclassified as nonsmokers in the first trimester.

However, oral fluid samples were obtained in each trimester of pregnancy, and ELISA assay was not used beyond the first trimester for these 42 women. On a related note, there may be some concern about potential bias in the cutoffs used for LC�CMSMS. The 5 ng/ml cutoff for LC�CMSMS was used to discriminate women who were designated as active smokers based on oral fluid samples from nonsmokers. There were only three women who had cotinine levels below this cutoff, and all had been assigned to the smoking group based on self-report. Thus, it is unlikely that the cigarette smoking mothers or those exposed to SHS were assigned to the nonexposed group because of the 5 ng/ml cutoff. The sample included in the analysis of change in SHS exposure over time was limited to 106 women who had completed all three trimester AV-951 interviews. Although we examined differences between women with complete data compared to those who had not yet completed all three interviews, there is always the possibility that this group differed from the overall sample on some unmeasured variables.