Ashford Kristin B, Blair Lisa M, McCubbin Andrea K, Wiggins Amanda T, Rayens Mary Kay, Hahn Ellen J
Perinatal Research and Wellness Center, University of Kentucky College of Nursing, Lexington, KY.
Perinatal Research and Wellness Center, University of Kentucky College of Nursing, Lexington, KY.
Am J Obstet Gynecol. 2022 Nov;227(5):767.e1-767.e10. doi: 10.1016/j.ajog.2022.07.058. Epub 2022 Aug 4.
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.
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.
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.
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.
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.
孕期吸烟和产前接触二手烟会增加早产风险。由于肯塔基州的吸烟率在美国排名第二，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。
本研究利用州级活产数据和县级市级无烟立法状况，评估无烟法律的存在和力度与早产可能性之间的关联。此外，本研究假设，与生活在无烟法律薄弱或中等（即有豁免规定、不涵盖所有工作场所和封闭公共场所的无烟法律）或没有无烟法律的县的孕妇相比，生活在有全面市级无烟法律、禁止在所有工作场所和封闭公共场所吸烟的县的孕妇早产的可能性更低。
利用肯塔基州生命统计办公室2004年至2020年出生年份的活产数据，共记录了894,372例活产，表明生育者年龄在18至49岁之间且是肯塔基州居民；这些活产构成了研究样本。由于出生记录除出生年份外进行了时间去识别处理，所以在模型中，将给定日历年度实施的市政条例编码为从下一个日历年度开始存在。这种滞后法律惯例最大限度地提高了纳入研究的孕妇在孕期至少一部分时间接触无烟政策的可能性。采用多水平逻辑回归评估无烟条例对早产可能性的影响，将个人和县级变量作为潜在协变量纳入，孕妇嵌套在居住县内。使用SAS（版本9.4；SAS Institute，卡里，北卡罗来纳州）进行数据分析，α水平为0.05。
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至24岁；优势比[95%置信区间]：25至34岁为1.02[1.01 - 1.04]，35至49岁为1.27[1.24 - 1.31]）；有早产史（优势比，4.65；95%置信区间，4.53 - 4.78）；以及孕前吸烟（优势比，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条例的县的孕妇低9%（优势比，0.91；95%置信区间，0.89 - 0.94；P <.001）。生活在无烟法律中等或薄弱的县的孕妇与居住县没有任何无烟条例保护的孕妇相比，早产可能性没有差异。
本研究表明，全面的市级无烟法律与降低早产风险相关，而中等或薄弱的无烟法律则不然。这些发现对公共卫生政策具有重要意义，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。
