Secondhand smoke (SHS) contains many toxic chemicals that can be detrimental to an infant’s health (Centers for Disease Control and Prevention, 2006). Infants who are exposed to SHS are at increased risk of respiratory tract and ear infections and Sudden Infant Death Syndrome (Centers for Disease Control and Prevention, 2006). In 2010, nearly 16% of women smoked after delivery, ranging from 7.2% (Utah) to 37.5% (West Virginia) (Tong et al., 2013). Because infants spend a substantial amount of time at home, complete smoke-free home rules (i.e., no smoking by anyone anywhere in the home at any time) should be encouraged (American Academy of Pediatrics, 2009).

Beginning in 2009, the Pregnancy Risk Assessment Monitoring System (PRAMS), a state-based surveillance system of maternal behaviors and attitudes administered 2–6 months after delivery, asked whether women had a complete smoke-free home rule at the time of survey administration in all participating states (Centers for Disease Control and Prevention, 2012). Only a small number of states asked this question prior to 2009, and a previous study of smoke-free home rules in only 5 states during 2004–2008 has been published (Gibbs et al., 2012). However, state-specific estimates of the percentage of women who have complete smoke-free home rules have not been previously reported from all PRAMS states and with more recent data.

The study objectives were to calculate state-specific prevalence estimates of complete smoke-free home rules among postpartum women in 26 PRAMS states and New York City in 2010, the most recent data available, and describe women who had complete smoke-free home rules by selected characteristics. These data can be used to inform state efforts to encourage 100% smoke-free home rules among postpartum women.

PRAMS is an ongoing state- and population-based surveillance system among women who delivered live-born infants in the United States. Details concerning the PRAMS methodology have been described elsewhere (Shulman et al., 2006). Briefly, at each site, a monthly stratified sample of 100–300 new mothers is selected systematically from birth certificates. Data are weighted to represent all women with live births in each site. Sites were included for analysis if the overall weighted response rate for a given site was ≥65% in 2010: Alaska, Arkansas, Colorado, Delaware, Georgia, Hawaii, Maine, Maryland, Massachusetts, Michigan, Minnesota, Missouri, Nebraska, New Jersey, New York, Ohio, Oklahoma, Oregon, Pennsylvania, Rhode Island, Texas, Utah, Vermont, Washington, West Virginia, Wyoming and New York City (NYC). The Centers for Disease Control and Prevention Institutional Review Board approved the PRAMS protocol; all sites approved the study plan.

Women’s report of having complete smoke-free home rules after delivery was determined from: “Which of the following statements best describes the rules about smoking inside your home now?” Respondents were categorized as having complete rules (“no one was allowed to smoke anywhere inside my home”) or partial/no rules (“smoking was allowed in some rooms or at some times” or “smoking was permitted anywhere inside my home”).

Prevalence and 95% confidence intervals (CIs) were estimated for each site. Data were aggregated to assess differences in prevalence by selected characteristics using Chi-square tests at P ≤ 0.05. We calculated adjusted prevalence ratios (APRs) and 95% CIs using multivariable logistic regression as described by Bieler et al. (2010). The analyses were conducted in 2013 using SAS version 9.3 and SUDAAN version 11 to account for the complex survey design of PRAMS (SAS, version 9.3, 2012; SUDAAN, version 11.0, 2012).

Of 38,255 women with available data, records were excluded if data on smoke-free home rules were missing (n = 557 [1.5%]). The final sample included 37,698 women. For other variables, the percentage of respondents who lacked data ranged from 0.02% (age) to 7.6% (income). Among PRAMS respondents, the average infant age was 117 days (range: 103 [Vermont]–170 [Georgia]). The data were weighted to account for sampling, nonresponse, and noncoverage and represent 52% of U.S. live births.

Based on aggregated data from 26 states and NYC, most women were aged 25–34 years (54.0%), non-Hispanic white (56.8%) and had more than 12 years of education (56.3%). The data were weighted to represent 1,916,846 women who delivered live births in the study states (Table 1). The total percentage of women who reported complete smoke-free home rules was 93.6% (95% CI: 93.1–94.1), and partial or no rules was 6.4% (95% CI: 5.9–6.9) (Table 1). Thus, an estimated 122,379 infants were in homes with partial or no smoke-free home rule. State-specific estimates of reporting complete rules ranged from 86.8% (West Virginia) to 98.6% (Utah).

Subgroups with the lowest prevalence of having complete smoke-free home rules after delivery were women who smoked during pregnancy and postpartum (77.6%), had never initiated breastfeeding (86.8%), were non-Hispanic Black (86.8%), were <20 years of age (87.1%), had <$15,000 annual income (87.6%), had <12 years of education (88.6%), were unmarried (88.6%), initiated prenatal care in the third trimester or had no prenatal care (88.8%), had Medicaid coverage during pregnancy or at delivery (89.7%), had an unintended pregnancy (90.3%), or were enrolled in WIC during pregnancy (90.6%) (Table 2). No significant differences in prevalence of complete rules were observed by parity or infant age.

After adjustment, the strongest association was found for women who smoked during and after pregnancy (APR, 0.90 [95% CI: 0.88–0.92]), and they were less likely to have a complete rule compared to nonsmokers. Groups more likely to have complete rules were ≥35 years, of Hispanic ethnicity, had >12 years of education, were married, were normal weight, and breastfed their infants ≥10 weeks, though these associations were weak.

Overall, the majority of postpartum women (93.6%) reported having complete smoke-free home rules after delivery, higher than the national estimate for all households (81.1%) (King et al., 2013). These data suggest that women with infants may have heightened awareness of the need for 100% smoke-free environments. However, we found disparities by state and among certain sub-groups.

State-specific differences may be a result of variation in state efforts to promote smoke-free environments, such as through media and educational campaigns. As of 2013, 26 states and the District of Columbia (Centers for Disease Control and Prevention, 2013) and 593 U.S. municipalities (American for Nonsmokers’ Rights Foundations, 2013) have implemented comprehensive laws that completely eliminate smoking in private workplaces, restaurants, and bars. Studies have suggested that residents of jurisdictions with comprehensive smoke-free laws are more likely to adopt household rules making homes and vehicles smoke-free, perhaps, because of greater awareness of the health risks of SHS and changes in social norms regarding the acceptability of smoking around nonsmokers (Cheng et al., 2011, 2013). Consistent with these findings, our study states with the highest prevalence estimates of complete smoke-free home rules also had comprehensive state smoke-free laws. Despite the high prevalence of complete rules in our population, in multi-unit housing, SHS can infiltrate other units, and children living in multi-unit housing are vulnerable to SHS exposure, even if no one in their household smokes (Wilson et al., 2011). Thus, educational initiatives encouraging adoption of smoke-free home rules and smoke-free policies in all homes including multi-unit housing are needed.

In our study, we found that smoking during and after pregnancy was the strongest predictor of not having complete smoke-free home rules even after adjusting for other maternal characteristics. These findings are consistent with a previous analysis of the 2004–2008 PRAMS data from 5 states (Gibbs et al., 2012). Having smoke-free home rules has been shown to reduce SHS exposure and increase smoking cessation (Centers for Disease Control and Prevention, 2006; Messer et al., 2008) even among low-income populations (Vijayaraghavan et al., 2013). Thus, clinicians or other providers who see women during and after pregnancy can educate parents, particularly smokers, about the adverse health effects of SHS for infants and encourage them to stay quit and make their homes 100% smoke-free.

The strengths of this study is that it is the largest study of smoke free home rules among postpartum women to-date, and the results are representative of 26 states and NYC, which constitute approximately half of all U.S. live births. This study has at least two limitations. First, having a home rule was self-reported, and prevalence could have been overestimated. However, parental report of having smoke-free home rules has been found to correlate with SHS exposure biomarkers in children (Hovell et al., 2000; Spencer et al., 2005). Also, these results may not be generalizable beyond the PRAMS sites included in this analysis.

Of the 1.9 million births that our study population represents, an estimated 120,000 infants are in homes with partial or no smoke-free home rules; half of those infants’ mothers smoked after delivery, exposing their infants to SHS. Efforts are needed to educate women during and after pregnancy and their families of the importance of adopting 100% smoke-free rules in homes and other private settings to protect infants’ health and well-being.