Background

Smoking during pregnancy and prenatal secondhand smoke exposure increase the risk of preterm birth. As Kentucky has the second highest rate of smoking in the United States and no statewide smoke-free law, an examination of the effect of municipal smoke-free legislation on preterm birth is warranted.

Objective

This study used state-level live birth data and county-level municipal smoke-free legislation status to assess the association between the presence and strength of smoke-free laws and the likelihood of preterm birth. Moreover, this study hypothesized that pregnant persons living in counties with comprehensive municipal smoke-free laws prohibiting smoking inside all workplaces and enclosed public places would exhibit a lower likelihood of preterm birth than those living in counties with weak or moderate laws (ie, smoke-free laws with exemptions that do not cover all workplaces and enclosed public places) or no smoke-free law.

Study Design

Using live birth data from the Kentucky Office of Vital Statistics with birth years ranging from 2004 to 2020, a total of 894,372 live births were recorded that indicated that a childbearing person was between the ages of 18 and 49 years and a resident of Kentucky; these live births formed the sample for the study. Municipal ordinances implemented during a given calendar year were coded in the model as present starting with the following calendar year, as the birth records were time deidentified except for the year of birth. This lagged law convention maximized the likelihood that pregnant persons included in the study were exposed to the smoke-free policy for at least a portion of their pregnancy. Multilevel logistic regression was used to assess the effect of smoke-free ordinances on the likelihood of preterm birth, with personal- and county-level variables included as potential covariates and pregnant persons nested within the county of residence. Data analysis was conducted using SAS (version 9.4; SAS Institute, Cary, NC), with an alpha level of .05.

Results

Nearly all personal-level variables were associated with preterm birth status. Personal factors associated with an increased likelihood of preterm birth included being older (relative to 18–24 years old; odds ratios [95% confidence intervals]: 1.02 [1.01–1.04] and 1.27 [1.24–1.31] for ages 25–34 and 35–49 years, respectively); having a history of preterm birth (odds ratio, 4.65; 95% confidence interval, 4.53–4.78); and smoking before pregnancy (odds ratio, 1.14; 95% confidence interval, 1.12–1.16). Pregnant persons living in counties with comprehensive laws were 9% less likely to have a preterm birth than those living in counties without a smoke-free ordinance (odds ratio, 0.91; 95% confidence interval, 0.89–0.94; P<.001). There was no difference in the likelihood of preterm birth between those living in counties with moderate or weak laws and those unprotected by any smoke-free ordinance in their county of residence.

Conclusion

This study demonstrated that comprehensive municipal smoke-free laws are associated with reduced risk of preterm birth and that moderate or weak smoke-free laws are not. The findings have major implications for public health policy and underscore the potential influence of healthcare providers’ advocacy for strong smoke-free policies, prohibiting smoking in all workplaces (including restaurants, bars, and casinos), to support healthy pregnancies.

中文翻译：

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市政无烟法和早产

背景

怀孕期间吸烟和产前接触二手烟会增加早产的风险。由于肯塔基州的吸烟率位居美国第二，并且没有全州范围的无烟法律，因此有必要研究市级无烟立法对早产的影响。

客观的

这项研究使用州级活产数据和县级市无烟立法状况来评估无烟法律的存在和强度与早产可能性之间的关联。此外，这项研究假设，生活在具有全面的城市无烟法律禁止在所有工作场所和封闭的公共场所吸烟的县的孕妇，与生活在法律较弱或中等的县（即吸烟-自由法律（但不涵盖所有工作场所和封闭的公共场所）或没有无烟法律。

学习规划

使用肯塔基州人口统计办公室的活产数据，出生年份为 2004 年至 2020 年，总共记录了 894,372 名活产婴儿，表明育龄者年龄在 18 岁至 49 岁之间，并且是肯塔基州居民；这些活产婴儿构成了研究的样本。在给定日历年中实施的市政法令在模型中被编码为从下一个日历年开始存在，因为除出生年份外，出生记录均已取消时间识别。这一滞后的法律惯例最大限度地提高了参与研究的孕妇至少在怀孕的一部分时间里接触无烟政策的可能性。使用多级逻辑回归来评估无烟法令对早产可能性的影响，其中个人和县级变量作为潜在协变量以及居住县内的孕妇。使用 SAS（9.4 版；SAS Institute，Cary，NC）进行数据分析，α 水平为 0.05。

结果

几乎所有个人层面的变量都与早产状况相关。与早产可能性增加相关的个人因素包括年龄较大（相对于 18-24 岁；比值比 [95% 置信区间]：25-34 岁为 1.02 [1.01-1.04] 和 1.27 [1.24-1.31]，分别为 35-49 岁）；有早产史（优势比，4.65；95% 置信区间，4.53–4.78）；怀孕前吸烟（比值比，1.14；95% 置信区间，1.12–1.16）。生活在有全面法律的县的孕妇早产的可能性比生活在没有无烟法令的县的孕妇低 9%（比值比，0.91；95% 置信区间，0.89–0.94；P <.001 ）。居住在法律中等或薄弱县的人与居住县未受任何无烟法令保护的人相比，早产的可能性没有差异。

结论

这项研究表明，全面的城市无烟法与降低早产风险相关，而中等或弱的无烟法则不然。研究结果对公共卫生政策具有重大影响，并强调了医疗保健提供者倡导强有力的无烟政策、禁止在所有工作场所（包括餐馆、酒吧和赌场）吸烟以支持健康怀孕的潜在影响。