A new study from Duke Health has found pregnant women experienced less secondhand smoke exposure since the 2009 passage of the 'smoking ban' in North Carolina, which outlawed smoking inside public places such as bars and restaurants. The research was published online in the International Journal of Environmental Research and Public Health.

Although overall, exposure has been reduced, the study identified racial and socioeconomic disparities among those who still are affected at home, at work and in their communities -- specifically women who are African American, women with less education, and those who are unmarried.

The data comes from 668 women who enrolled in the study between 2005 and 2011. Their secondhand smoke exposure was measured by the presence of cotinine, a biomarker found in blood plasma that indicates nicotine exposure within the previous 48 to 72 hours.

The blood tests indicated that most non-smoking pregnant women were not exposed to nicotine in the days prior to being tested for the study. Although some women still had exposure after the passage of the ban, average levels of cotinine in their blood were lower than those before the ban.

The study focused on the Southeast, a part of the U.S. that has some of the highest rates for poor perinatal outcomes, said the study's lead author Julia Schechter, Ph.D., a clinical psychologist and assistant professor at Duke Health. Smoking and secondhand smoke exposure can contribute to complications including miscarriage, low birth weight, early birth and learning and behavioral deficiencies in children.

"North Carolina still doesn't have a fully comprehensive smoking ban," Schechter said. "The findings are encouraging, but we still aren't completely smoke free." Considering many communities in the region have roots in tobacco farming and production, continued policy change may be particularly challenging, she said.

Schechter and colleagues are also conducting research on potential links between smoke exposure during pregnancy and ADHD.

In addition to Schechter, study authors include Susan K. Murphy, Junfeng (Jim) Zhang, and Scott H. Kollins of Duke, Bernard F. Fuemmeler of Virginia Commonwealth University, and Cathrine Hoyo of N.C. State University.

The research was supported by National Institute of Environmental Health Sciences of the National Institutes of Health (P01ES022831, R21ES014947, R01ES016772, K24DA023464, P30ES025128) and by the U.S. Environmental Protection Agency (RD-83543701). Additional support was provided by the National Center for Research Resources, a component of the NIH and NIH Roadmap for Medical Research (UL1TR001117).